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119-458: Provadia served as a customs point since ancient times. It is well known for salty mineral waters , its mild climate and a total of 70 km of caves in the surrounding mountain walls. It can be reached by train from Sofia or Varna and there are also hourly buses from and to Varna, and a sophisticated road system. Provadia is the site of Solnitsata , Europe's oldest prehistoric town. Excavations on city walls that started in 2005 reveal

238-524: A solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form. The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite ) or organic compounds in the sense of chemistry (such as mellite ). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite ) that also occur in rocks. The concept of mineral

357-611: A 10,000-strong Byzantine army near the city in 1279. During the Second Bulgarian Empire it was the seat of a metropolitan in the 14th century. Ovech was captured by the Ottomans in 1388 after a long siege. In the 17th and 18th century Provadia was a commercial centre of the Ottoman Empire and was inhabited by many Jewish and Ragusan merchants. A 16th-17th-century Dubrovnik -style church still stands in

476-585: A bend in the middle that is caused by start of the twin. Penetration twins consist of two single crystals that have grown into each other; examples of this twinning include cross-shaped staurolite twins and Carlsbad twinning in orthoclase. Cyclic twins are caused by repeated twinning around a rotation axis. This type of twinning occurs around three, four, five, six, or eight-fold axes, and the corresponding patterns are called threelings, fourlings, fivelings , sixlings, and eightlings. Sixlings are common in aragonite. Polysynthetic twins are similar to cyclic twins through

595-417: A bigger coordination numbers because of the increase in relative size as compared to oxygen (the last orbital subshell of heavier atoms is different too). Changes in coordination numbers leads to physical and mineralogical differences; for example, at high pressure, such as in the mantle , many minerals, especially silicates such as olivine and garnet , will change to a perovskite structure , where silicon

714-432: A chemical compound occurs naturally with different crystal structures, each structure is considered a different mineral species. Thus, for example, quartz and stishovite are two different minerals consisting of the same compound, silicon dioxide . The International Mineralogical Association (IMA) is the generally recognized standard body for the definition and nomenclature of mineral species. As of November 2024 ,

833-473: A distinct mineral: The details of these rules are somewhat controversial. For instance, there have been several recent proposals to classify amorphous substances as minerals, but they have not been accepted by the IMA. The IMA is also reluctant to accept minerals that occur naturally only in the form of nanoparticles a few hundred atoms across, but has not defined a minimum crystal size. Some authors require

952-438: A fertilizer, applying a moderate concentration helps avoid potential toxicity; typically, 1–3 grams (0.035–0.106 oz) per liter is considered safe and effective for most plants. Sodium chloride is one of the largest volume inorganic raw materials. It is a feedstock in the production of caustic soda and chlorine . These are used in the manufacture of PVC , paper pulp and many other inorganic and organic compounds. Salt

1071-443: A healthy level of sodium intake of between 4 and 5 grams (equivalent to 10-13 g salt) a day. One of the two most prominent dietary risks for disability in the world are diets high in sodium. Only a small percentage of the salt manufactured in the world is used in food. The remainder is used in agriculture, water treatment, chemical production, de-icing, and other industrial use cases. In the practice of watering plants with salt as

1190-422: A high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments. Human salt taste is detected by sodium taste receptors present in taste bud cells on the tongue. Human sensory taste testing studies have shown that proteolyzed forms of epithelial sodium channel (ENaC) function as the human salt taste receptor. Table salt

1309-463: A key to defining a substance as a mineral. A 2011 article defined icosahedrite , an aluminium-iron-copper alloy, as a mineral; named for its unique natural icosahedral symmetry , it is a quasicrystal . Unlike a true crystal, quasicrystals are ordered but not periodic. A rock is an aggregate of one or more minerals or mineraloids. Some rocks, such as limestone or quartzite , are composed primarily of one mineral – calcite or aragonite in

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1428-522: A metaphor. Uses include the tale of how Lot's wife is turned into a pillar of salt when looking back at the cities of Sodom and Gomorrah as they are destroyed. In the New Testament , Jesus refers to his followers as the " salt of the earth ". In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water. Salt is an auspicious substance in Hinduism and

1547-461: A mildly "fishy" or "sea-air" odour, the latter from organobromine compounds . Sediments, the proportion of which varies with the source, give the salt a dull grey appearance. Since taste and aroma compounds are often detectable by humans in minute concentrations, sea salt may have a more complex flavour than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavours would likely be overwhelmed by those of

1666-409: A mineral defines how much it can resist scratching or indentation. This physical property is controlled by the chemical composition and crystalline structure of a mineral. The most commonly used scale of measurement is the ordinal Mohs hardness scale, which measures resistance to scratching. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc,

1785-535: A salt spring in Lunca , Neamț County , Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract salt as far back as 6050 BC. The salt extracted from this operation may have directly correlated with the rapid growth of this society's population soon after production began. The harvest of salt from

1904-514: A salty bread or to add salt to the bread if this bread is unsalted when doing Kiddush for Shabbat . It is customary to spread some salt over the bread or to dip the bread in a little salt when passing the bread around the table after the Kiddush. To preserve the covenant between their people and God, Jews dip the Sabbath bread in salt. Salt plays a role within different Christian traditions. It

2023-426: A scrubbing agent when combined with oil. Salt is present in most foods , but in naturally occurring foodstuffs such as meats, vegetables and fruit, it is present in very small quantities. It is often added to processed foods (such as canned foods and especially salted foods , pickled foods , and snack foods or other convenience foods ), where it functions as both a preservative and a flavouring . Dairy salt

2142-432: A sedimentary mineral, and silicic acid ): Under low-grade metamorphic conditions, kaolinite reacts with quartz to form pyrophyllite (Al 2 Si 4 O 10 (OH) 2 ): As metamorphic grade increases, the pyrophyllite reacts to form kyanite and quartz: Alternatively, a mineral may change its crystal structure as a consequence of changes in temperature and pressure without reacting. For example, quartz will change into

2261-406: A tetrahedral fashion; on the other hand, graphite is composed of sheets of carbons in sp hybrid orbitals, where each carbon is bonded covalently to only three others. These sheets are held together by much weaker van der Waals forces , and this discrepancy translates to large macroscopic differences. Twinning is the intergrowth of two or more crystals of a single mineral species. The geometry of

2380-418: A town that dates back to between 4,700 BC and 4,200 BC. It is believed to have been the site of salt trading. Historical names of the medieval fortress, the ruins of which have been preserved until today, include Provat ( Byzantine Greek ), Ovech (Овеч, Bulgarian), Provanto ( Italian ) and Pravadı ( Turkish language ). The Greek name and its adaptations stem from the word πρόβατο, provato , "sheep", and

2499-935: A variety of its SiO 2 polymorphs , such as tridymite and cristobalite at high temperatures, and coesite at high pressures. Classifying minerals ranges from simple to difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex optical , chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming. Physical properties applied for classification include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, cleavage and fracture, and specific gravity. Other less general tests include fluorescence , phosphorescence , magnetism , radioactivity , tenacity (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids . Crystal structure results from

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2618-502: A variety of minerals because of the need to balance charges. Because the eight most common elements make up over 98% of the Earth's crust, the small quantities of the other elements that are typically present are substituted into the common rock-forming minerals. The distinctive minerals of most elements are quite rare, being found only where these elements have been concentrated by geological processes, such as hydrothermal circulation , to

2737-505: A virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated. The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. Salt evaporation ponds are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity. Away from

2856-595: A white mica, can be used for windows (sometimes referred to as isinglass), as a filler, or as an insulator. Ores are minerals that have a high concentration of a certain element, typically a metal. Examples are cinnabar (HgS), an ore of mercury; sphalerite (ZnS), an ore of zinc; cassiterite (SnO 2 ), an ore of tin; and colemanite , an ore of boron . Gems are minerals with an ornamental value, and are distinguished from non-gems by their beauty, durability, and usually, rarity. There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of

2975-439: A yellow colour. Folic acid helps prevent neural tube defects and anaemia, which affect young mothers, especially in developing countries. A lack of fluoride in the diet is the cause of a greatly increased incidence of dental caries . Fluoride salts can be added to table salt with the goal of reducing tooth decay, especially in countries that have not benefited from fluoridated toothpastes and fluoridated water. The practice

3094-707: Is a sedimentary rock composed primarily of organically derived carbon. In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals. The major examples of these are quartz, the feldspars , the micas , the amphiboles , the pyroxenes , the olivines , and calcite; except for the last one, all of these minerals are silicates. Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting. Commercially valuable minerals and rocks, other than gemstones, metal ores, or mineral fuels, are referred to as industrial minerals . For example, muscovite ,

3213-695: Is about 10 g per day, and it is higher than that in many countries in Eastern Europe and Asia. The high level of sodium in many processed foods has a major impact on the total amount consumed. In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what is found naturally in foodstuffs. Because consuming too much sodium increases risk of cardiovascular diseases , health organizations generally recommend that people reduce their dietary intake of salt. High sodium intake

3332-469: Is an important micronutrient for humans, and a deficiency of the element can cause lowered production of thyroxine ( hypothyroidism ) and enlargement of the thyroid gland ( endemic goitre ) in adults or cretinism in children. Iodized salt has been used to correct these conditions since 1924 and consists of table salt mixed with a minute amount of potassium iodide , sodium iodide , or sodium iodate . A small amount of dextrose may be added to stabilize

3451-561: Is associated with a greater risk of stroke , total cardiovascular disease and kidney disease . A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular disease by about 30 percent. In adults and children with no acute illness, a decrease in the intake of sodium from the typical high levels reduces blood pressure. A low sodium diet results in a greater improvement in blood pressure in people with hypertension . The World Health Organization recommends that adults should consume less than 2,000 mg of sodium (which

3570-420: Is contained in 5   g of salt) per day. Guidelines by the United States recommend that people with hypertension, African Americans, and middle-aged and older adults should limit consumption to no more than 1,500 mg of sodium per day and meet the potassium recommendation of 4,700 mg/day with a healthy diet of fruits and vegetables. While reduction of sodium intake to less than 2,300 mg per day

3689-428: Is distinct from rock , which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral or may be an aggregate of two or more different types of minerals, spacially segregated into distinct phases . Some natural solid substances without a definite crystalline structure, such as opal or obsidian , are more properly called mineraloids . If

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3808-419: Is dug out by the room and pillar method, where about half the material is left in place to support the upper levels. Extraction of Himalayan salt is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.The mine is also a major tourist attraction, receiving around a quarter of a million visitors a year. Salt has long held an important place in religion and culture. At

3927-693: Is either beneficial or harmful. Evidence shows a more complicated relationship between salt and cardiovascular disease. "The association between sodium consumption and cardiovascular disease or mortality is U-shaped, with increased risk at both high and low sodium intake." The findings showed that increased mortality from excessive salt intake was primarily associated with individuals with hypertension. The levels of increased mortality among those with restricted salt intake appeared to be similar regardless of blood pressure. This evidence shows that while those with hypertension should primarily focus on reducing sodium to recommended levels, all groups should seek to maintain

4046-448: Is in octahedral coordination. Other examples are the aluminosilicates kyanite , andalusite , and sillimanite (polymorphs, since they share the formula Al 2 SiO 5 ), which differ by the coordination number of the Al ; these minerals transition from one another as a response to changes in pressure and temperature. In the case of silicate materials, the substitution of Si by Al allows for

4165-539: Is made up of just under 40% sodium by weight, so a 6   g serving (1   teaspoon) contains about 2,400   mg of sodium. Sodium serves a vital purpose in the human body: via its role as an electrolyte, it helps nerves and muscles to function correctly, and it is one factor involved in the osmotic regulation of water content in body organs ( fluid balance ). Most of the sodium in the Western diet comes from salt. The habitual salt intake in many Western countries

4284-606: Is mandatory in the rite of the Tridentine Mass . Salt is used in the third item (which includes an Exorcism ) of the Celtic Consecration ( cf. Gallican Rite ) that is employed in the consecration of a church, and it is permitted to be added to the water "where it is customary" in the Roman Catholic rite of Holy water. The Bible makes multiple mentions of salt , both of the mineral itself and as

4403-547: Is more common in some European countries where water fluoridation is not carried out. In France , 35% of the table salt sold contains added sodium fluoride . Unrefined sea salt contains small amounts of magnesium and calcium halides and sulfates , traces of algal products , salt-resistant bacteria and sediment particles. The calcium and magnesium salts confer a faintly bitter overtone, and they make unrefined sea salt hygroscopic (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute

4522-401: Is more formally called table salt . In the form of a natural crystalline mineral, salt is also known as rock salt or halite . Salt is essential for life in general (being the source of the essential dietary minerals sodium and chlorine ), and saltiness is one of the basic human tastes . Salt is one of the oldest and most ubiquitous food seasonings , and is known to uniformly improve

4641-409: Is mostly sodium chloride (NaCl). Sea salt and mined salt may contain trace elements . Mined salt is often refined. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. When dissolved in water sodium chloride separates into Na and Cl ions, and the solubility is 359 grams per litre. From cold solutions, salt crystallises as

4760-464: Is named for Provadia. The current mayor of the town is Dimo Dimov, elected in . Provadia is the seat of Provadia municipality (part of Varna Province), which also includes the following 24 villages: 43°11′N 27°26′E  /  43.183°N 27.433°E  / 43.183; 27.433 Salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it

4879-408: Is possible for one element to be substituted for another. Chemical substitution will occur between ions of a similar size and charge; for example, K will not substitute for Si because of chemical and structural incompatibilities caused by a big difference in size and charge. A common example of chemical substitution is that of Si by Al , which are close in charge, size, and abundance in the crust. In

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4998-470: Is possible for two rocks to have an identical or a very similar bulk rock chemistry without having a similar mineralogy. This process of mineralogical alteration is related to the rock cycle . An example of a series of mineral reactions is illustrated as follows. Orthoclase feldspar (KAlSi 3 O 8 ) is a mineral commonly found in granite , a plutonic igneous rock . When exposed to weathering, it reacts to form kaolinite (Al 2 Si 2 O 5 (OH) 4 ,

5117-428: Is prepared by roasting salt in a bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to increase the anticlastogenic and antimutagenic properties of doenjang (a fermented bean paste). Kosher or kitchen salt has a larger grain size than table salt and is used in cooking. It can be useful for brining , in bread or pretzel making, and as

5236-435: Is recommended by developed countries, one review recommended that sodium intake be reduced to at least 1,200 mg (contained in 3   g of salt) per day, as a further reduction in salt intake led to a greater fall in systolic blood pressure for all age groups and ethnicities. Another review indicated that there is inconsistent/insufficient evidence to conclude that reducing sodium intake to lower than 2,300 mg per day

5355-556: Is refined by treatment with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then applied. Some salt is produced using the Alberger process , which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake. The Ayoreo , an indigenous group from the Paraguayan Chaco , obtain their salt from

5474-524: Is the angle opposite the a-axis, viz. the angle between the b and c axes): The hexagonal crystal family is also split into two crystal systems  – the trigonal , which has a three-fold axis of symmetry, and the hexagonal, which has a six-fold axis of symmetry. Chemistry and crystal structure together define a mineral. With a restriction to 32 point groups, minerals of different chemistry may have identical crystal structure. For example, halite (NaCl), galena (PbS), and periclase (MgO) all belong to

5593-405: Is the hardest natural substance, has an adamantine lustre, and belongs to the isometric crystal family, whereas graphite is very soft, has a greasy lustre, and crystallises in the hexagonal family. This difference is accounted for by differences in bonding. In diamond, the carbons are in sp hybrid orbitals, which means they form a framework where each carbon is covalently bonded to four neighbours in

5712-456: Is typical of garnet, prismatic (elongated in one direction), and tabular, which differs from bladed habit in that the former is platy whereas the latter has a defined elongation. Related to crystal form, the quality of crystal faces is diagnostic of some minerals, especially with a petrographic microscope. Euhedral crystals have a defined external shape, while anhedral crystals do not; those intermediate forms are termed subhedral. The hardness of

5831-409: Is used as a flux in the production of aluminium . For this purpose, a layer of melted salt floats on top of the molten metal and removes iron and other metal contaminants. It is used in the manufacture of soaps and glycerine , where it is used to saponify fats. As an emulsifier, salt is used in the manufacture of synthetic rubber , and another use is in the firing of pottery , when salt added to

5950-461: Is used extensively in cooking as a flavouring, and in cooking techniques such as with salt crusts and brining . The main sources of salt in the Western diet, apart from direct use, are bread and cereals, meat, and dairy products. In many East Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as soy sauce , fish sauce and oyster sauce tend to have

6069-468: Is used in ceremonies like house-warmings and weddings. In Jainism , devotees lay an offering of raw rice with a pinch of salt before a deity to signify their devotion and salt is sprinkled on a person's cremated remains before the ashes are buried. Salt is believed to ward off evil spirits in Mahayana Buddhist tradition, and when returning home from a funeral , a pinch of salt is thrown over

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6188-441: Is used in many cuisines, and it is often found in salt shakers on diners' eating tables for their personal use on food. Salt is also an ingredient in many manufactured foodstuffs. Table salt is a refined salt containing about 97 to 99 percent sodium chloride . Usually, anticaking agents such as sodium aluminosilicate or magnesium carbonate are added to make it free-flowing. Iodized salt , containing potassium iodide ,

6307-477: Is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from salt mines , and by the evaporation of seawater ( sea salt ) and mineral-rich spring water in shallow pools. The greatest single use for salt (sodium chloride) is as a feedstock for the production of chemicals. It is used to produce caustic soda and chlorine , and in the manufacture of products such as polyvinyl chloride , plastics , and paper pulp . Of

6426-617: Is used in the preparation of butter and cheese products. As a flavouring, salt enhances the taste of other foods by suppressing the bitterness of those foods making them more palatable and relatively sweeter. Before the advent of electrically powered refrigeration , salting was one of the main methods of food preservation . Thus, herring contains 67 mg sodium per 100 g, while kipper , its preserved form, contains 990 mg. Similarly, pork typically contains 63 mg while bacon contains 1,480 mg, and potatoes contain 7 mg but potato crisps 800 mg per 100 g. Salt

6545-434: Is widely available. Some people put a desiccant , such as a few grains of uncooked rice or a saltine cracker , in their salt shakers to absorb extra moisture and help break up salt clumps that may otherwise form. Some table salt sold for consumption contains additives that address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary from country to country. Iodine

6664-618: The CIPW norm , which gives reasonable estimates for volcanic rock formed from dry magma. The chemical composition may vary between end member species of a solid solution series. For example, the plagioclase feldspars comprise a continuous series from sodium -rich end member albite (NaAlSi 3 O 8 ) to calcium -rich anorthite (CaAl 2 Si 2 O 8 ) with four recognized intermediate varieties between them (given in order from sodium- to calcium-rich): oligoclase , andesine , labradorite , and bytownite . Other examples of series include

6783-590: The Committee on Toxicity in 1988. Other anticaking agents sometimes used include tricalcium phosphate , calcium or magnesium carbonates, fatty acid salts ( acid salts ), magnesium oxide , silicon dioxide , calcium silicate , sodium aluminosilicate and calcium aluminosilicate . Both the European Union and the United States Food and Drug Administration permitted the use of aluminium in

6902-622: The German word Salz , salt. Hallstatt was the site of the world's first salt mine . The town gave its name to the Hallstatt culture that began mining for salt in the area in about 800 BC. Around 400 BC, the townsfolk, who had previously used pickaxes and shovels , began open pan salt making . During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries. The word salary comes from

7021-692: The Latin word for salt. The reason for this is unknown; a persistent modern claim that the Roman Legions were sometimes paid in salt is baseless. The word salad literally means "salted", and comes from the ancient Roman practice of salting leaf vegetables . Wars have been fought over salt. Venice won a war with Genoa over the product, and it played a role in the American Revolution . Cities on overland trade routes grew rich by levying duties , and towns like Liverpool flourished on

7140-413: The dihydrate NaCl·2H 2 O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is around 108.7 °C (227.7 °F). Salt is essential to the health of humans and other animals, and it is one of the five basic taste sensations . Salt

7259-496: The hydrosphere , atmosphere , and biosphere . The group's scope includes mineral-forming microorganisms, which exist on nearly every rock, soil, and particle surface spanning the globe to depths of at least 1600 metres below the sea floor and 70 kilometres into the stratosphere (possibly entering the mesosphere ). Biogeochemical cycles have contributed to the formation of minerals for billions of years. Microorganisms can precipitate metals from solution , contributing to

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7378-826: The obsidian trade in Anatolia in the Neolithic Era . Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, and salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar , glass, and the dye Tyrian purple ; the Phoenicians traded Egyptian salted fish and salt from North Africa throughout their Mediterranean trade empire. Herodotus described salt trading routes across Libya back in

7497-473: The olivine group . Besides the essential chemical composition and crystal structure, the description of a mineral species usually includes its common physical properties such as habit , hardness , lustre , diaphaneity , colour, streak , tenacity , cleavage , fracture , parting, specific gravity , magnetism , fluorescence , radioactivity , as well as its taste or smell and its reaction to acid . Minerals are classified by key chemical constituents;

7616-454: The tanning of hides, the preservation of meat and fish and the canning of meat and vegetables. Food-grade salt accounts for only a small part of salt production in industrialized countries (7% in Europe), although worldwide, food uses account for 17.5% of total production. In 2018, total world production of salt was 300 million tonnes , the top six producers being China (68 million),

7735-665: The 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at Ostia to the capital. In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in Abyssinia . The Tuareg have traditionally maintained routes across the Sahara especially for the transportation of salt by Azalai (salt caravans). The caravans still cross

7854-455: The 78 mineral classes listed in the Dana classification scheme. Skinner's (2005) definition of a mineral takes this matter into account by stating that a mineral can be crystalline or amorphous. Although biominerals are not the most common form of minerals, they help to define the limits of what constitutes a mineral proper. Nickel's (1995) formal definition explicitly mentioned crystallinity as

7973-474: The IMA recognizes 6,100 official mineral species. The chemical composition of a named mineral species may vary somewhat due to the inclusion of small amounts of impurities. Specific varieties of a species sometimes have conventional or official names of their own. For example, amethyst is a purple variety of the mineral species quartz . Some mineral species can have variable proportions of two or more chemical elements that occupy equivalent positions in

8092-431: The IMA's decision to exclude biogenic crystalline substances. For example, Lowenstam (1981) stated that "organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere." Skinner (2005) views all solids as potential minerals and includes biominerals in the mineral kingdom, which are those that are created by the metabolic activities of organisms. Skinner expanded

8211-455: The IMA. They are most commonly named after a person , followed by discovery location; names based on chemical composition or physical properties are the two other major groups of mineral name etymologies. Most names end in "-ite"; the exceptions are usually names that were well-established before the organization of mineralogy as a discipline, for example galena and diamond . A topic of contention among geologists and mineralogists has been

8330-556: The Latin species , "a particular sort, kind, or type with distinct look, or appearance". The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth. The majority of minerals observed are derived from the Earth's crust . Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of

8449-460: The UK the recommended iodine content of iodized salt is 10–22 ppm. Sodium ferrocyanide , yellow prussiate of soda, is sometimes added to salt as an anticaking agent . Such anticaking agents have been added since at least 1911 when magnesium carbonate was first added to salt to make it flow more freely. The safety of sodium ferrocyanide as a food additive was found to be provisionally acceptable by

8568-490: The United States (42 million), India (29 million), Germany (13 million), Canada (13 million) and Australia (12 million). The manufacture of salt is one of the oldest chemical industries. A major source of salt is seawater, which has a salinity of approximately 3.5%. This means that there are about 35 g (1.2 oz) of dissolved salts , predominantly sodium ( Na ) and chloride ( Cl ) ions , per kilogram (2.2 lbs) of water. The world's oceans are

8687-488: The aluminium abundance is unusually high, the excess aluminium will form muscovite or other aluminium-rich minerals. If silicon is deficient, part of the feldspar will be replaced by feldspathoid minerals. Precise predictions of which minerals will be present in a rock of a particular composition formed at a particular temperature and pressure requires complex thermodynamic calculations. However, approximate estimates may be made using relatively simple rules of thumb , such as

8806-429: The annual global production of around three hundred million tonnes , only a small percentage is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use. Edible salt is sold in forms such as sea salt and table salt, the latter of which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency . As well as its use in cooking and at

8925-692: The ash produced by burning the timber of the Indian salt tree ( Maytenus vitis-idaea ) and other trees. The largest mine operated by underground workings in the world is the Sifto mine, located mostly 550 meters below Lake Huron, in Goderich, Ontario (Canada). About seven million tons of salt are extracted from it annually. The Khewra Salt Mine in Pakistan has nineteen storeys, eleven of which are underground, and 400 km (250 mi) of passages. The salt

9044-671: The availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata , in Bulgaria , which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC. Salt was the best-known food preservative, especially for meat, for many thousands of years. A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to

9163-449: The bulk chemistry of the parent body. For example, in most igneous rocks, the aluminium and alkali metals (sodium and potassium) that are present are primarily found in combination with oxygen, silicon, and calcium as feldspar minerals. However, if the rock is unusually rich in alkali metals, there will not be enough aluminium to combine with all the sodium as feldspar, and the excess sodium will form sodic amphiboles such as riebeckite . If

9282-424: The case of limestone, and quartz in the latter case. Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar , and plagioclase feldspar . The other minerals in the rock are termed accessory minerals , and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal

9401-400: The coast natives lost their previous profits; as of the late 1950s, sea salt was still the currency best appreciated in the interior. Salzburg , Hallstatt , and Hallein lie within 17 km (11 mi) of each other on the river Salzach in central Austria in an area with extensive salt deposits. Salzach means "salt river" while Salzburg means "salt castle", both taking their names from

9520-415: The coordination of the silicate is by a number: in the case of the silica tetrahedron, the silicon is said to have a coordination number of 4. Various cations have a specific range of possible coordination numbers; for silicon, it is almost always 4, except for very high-pressure minerals where the compound is compressed such that silicon is in six-fold (octahedral) coordination with oxygen. Bigger cations have

9639-417: The crust by weight, are, in order of decreasing abundance: oxygen , silicon , aluminium , iron , magnesium , calcium , sodium and potassium . Oxygen and silicon are by far the two most important – oxygen composes 47% of the crust by weight, and silicon accounts for 28%. The minerals that form are those that are most stable at the temperature and pressure of formation, within the limits imposed by

9758-444: The desert from southern Niger to Bilma , although much of the trade now takes place by truck. Each camel takes two bales of fodder and two of trade goods northwards and returns laden with salt pillars and dates. In Gabon, before the arrival of Europeans, the coast people carried on a remunerative trade with those of the interior by the medium of sea salt. This was gradually displaced by the salt that Europeans brought in sacks, so that

9877-434: The difference in charge has to accounted for by making a second substitution of Si by Al . Coordination polyhedra are geometric representations of how a cation is surrounded by an anion. In mineralogy, coordination polyhedra are usually considered in terms of oxygen, due its abundance in the crust. The base unit of silicate minerals is the silica tetrahedron – one Si surrounded by four O . An alternate way of describing

9996-414: The dipyramidal point group. These differences arise corresponding to how aluminium is coordinated within the crystal structure. In all minerals, one aluminium ion is always in six-fold coordination with oxygen. Silicon, as a general rule, is in four-fold coordination in all minerals; an exception is a case like stishovite (SiO 2 , an ultra-high pressure quartz polymorph with rutile structure). In kyanite,

10115-517: The example of plagioclase, there are three cases of substitution. Feldspars are all framework silicates, which have a silicon-oxygen ratio of 2:1, and the space for other elements is given by the substitution of Si by Al to give a base unit of [AlSi 3 O 8 ] ; without the substitution, the formula would be charge-balanced as SiO 2 , giving quartz. The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na and Ca ; however,

10234-581: The export of salt extracted from the salt mines of Cheshire . Various governments have at different times imposed salt taxes on their peoples. The voyages of Christopher Columbus are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the French Revolution . After being repealed, this tax was reimposed by Napoleon when he became emperor to pay for his foreign wars , and

10353-478: The food ingredients. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases . Salts have diverse mineralities depending on their source, giving each a unique flavour. Fleur de sel , a natural sea salt from the surface of evaporating brine in salt pans, has a distinctive flavour varying with its source. In traditional Korean cuisine , so-called " bamboo salt "

10472-778: The formation of ore deposits. They can also catalyze the dissolution of minerals. Prior to the International Mineralogical Association's listing, over 60 biominerals had been discovered, named, and published. These minerals (a sub-set tabulated in Lowenstam (1981) ) are considered minerals proper according to Skinner's (2005) definition. These biominerals are not listed in the International Mineral Association official list of mineral names; however, many of these biomineral representatives are distributed amongst

10591-435: The furnace vaporises before condensing onto the surface of the ceramic material, forming a strong glaze . When drilling through loose materials such as sand or gravel, salt may be added to the drilling fluid to provide a stable "wall" to prevent the hole collapsing. There are many other processes in which salt is involved. These include its use as a mordant in textile dying, to regenerate resins in water softening, for

10710-410: The generic AX 2 formula; these two groups are collectively known as the pyrite and marcasite groups. Polymorphism can extend beyond pure symmetry content. The aluminosilicates are a group of three minerals – kyanite , andalusite , and sillimanite  – which share the chemical formula Al 2 SiO 5 . Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to

10829-451: The hexaoctahedral point group (isometric family), as they have a similar stoichiometry between their different constituent elements. In contrast, polymorphs are groupings of minerals that share a chemical formula but have a different structure. For example, pyrite and marcasite , both iron sulfides, have the formula FeS 2 ; however, the former is isometric while the latter is orthorhombic. This polymorphism extends to other sulfides with

10948-651: The iodine. Iodine deficiency affects about two billion people around the world and is the leading preventable cause of intellectual disabilities . Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used. The amount of iodine and the specific iodine compound added to salt varies. In the United States , the Food and Drug Administration (FDA) recommends 150 micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in

11067-412: The latter two compounds. In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates iron deficiency anaemia , which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is ferrous fumarate . Another additive, especially important for pregnant women, is folic acid (vitamin B 9 ), which gives the table salt

11186-421: The left shoulder as this prevents evil spirits from entering the house. In Shinto , Shio ( 塩 , lit. "salt" ) is used for ritual purification of locations and people ( harae , specifically shubatsu ), and small piles of salt are placed in dishes by entrances to wardi off evil and to attract patrons. Mineral In geology and mineralogy , a mineral or mineral species is, broadly speaking,

11305-461: The material to be a stable or metastable solid at room temperature (25 °C). However, the IMA only requires that the substance be stable enough for its structure and composition to be well-determined. For example, it has recently recognized meridianiite (a naturally occurring hydrate of magnesium sulfate ) as a mineral, even though it is formed and stable only below 2 °C. As of November 2024 , 6,100 mineral species are approved by

11424-680: The medieval Bulgarian name corresponds directly (being derived from овца, ovtsa , with the same meaning). The fortress is open for visitors. During the Middle Ages the town was a key centre of the First Bulgarian Empire with an important monastery at the modern village of Ravna, the church of which was consecrated on 23 April 897, and a major scriptorium of the Preslav Literary School . The rebel leader and subsequently emperor of Bulgaria Ivailo defeated

11543-433: The mineral's structure; for example, the formula of mackinawite is given as (Fe,Ni) 9 S 8 , meaning Fe x Ni 9- x S 8 , where x is a variable number between 0 and 9. Sometimes a mineral with variable composition is split into separate species, more or less arbitrarily, forming a mineral group ; that is the case of the silicates Ca x Mg y Fe 2- x - y SiO 4 ,

11662-494: The most common gemstones. Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum , Al 2 O 3 . The first known use of the word "mineral" in the English language ( Middle English ) was the 15th century. The word came from Medieval Latin : minerale , from minera , mine, ore. The word "species" comes from

11781-428: The most encompassing of these being the six crystal families. These families can be described by the relative lengths of the three crystallographic axes, and the angles between them; these relationships correspond to the symmetry operations that define the narrower point groups. They are summarized below; a, b, and c represent the axes, and α, β, γ represent the angle opposite the respective crystallographic axis (e.g. α

11900-525: The nearby village of Dobrina . South of Provadia lies the largest rock salt mine in Bulgaria, which is believed to be virtually inexhaustible with a salt dome up to 3900 m high, and has been sporadically exploited for some 7500 years but industrially, through leaching, only since the 1960s; now it is part of Solvay Sodi AD in Devnya under the name Provadsol AD. Some of the leaching caverns are used for

12019-402: The olivine series of magnesium-rich forsterite and iron-rich fayalite, and the wolframite series of manganese -rich hübnerite and iron-rich ferberite . Chemical substitution and coordination polyhedra explain this common feature of minerals. In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system. As a result, it

12138-771: The one at Karlovy Vary . Places of interest include the Lambova Kashta ethnographical complex and ethnographical collections in Dobrina and Manastir villages, as well as cave monasteries and the ruins of the 9-10th-century Ravna Monastery , one of the most important centres of the Preslav Literary School, dubbed "language laboratory" by Umberto Eco for its graffiti by common folks in several languages and alphabets. Provadiya Hook in Greenwich Island , South Shetland Islands , Antarctica

12257-622: The orderly geometric spatial arrangement of atoms in the internal structure of a mineral. This crystal structure is based on regular internal atomic or ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic and can be determined by X-ray diffraction. Minerals are typically described by their symmetry content. Crystals are restricted to 32 point groups , which differ by their symmetry. These groups are classified in turn into more broad categories,

12376-563: The point where they can no longer be accommodated in common minerals. Changes in temperature and pressure and composition alter the mineralogy of a rock sample. Changes in composition can be caused by processes such as weathering or metasomatism ( hydrothermal alteration ). Changes in temperature and pressure occur when the host rock undergoes tectonic or magmatic movement into differing physical regimes. Changes in thermodynamic conditions make it favourable for mineral assemblages to react with each other to produce new minerals; as such, it

12495-447: The presence of repetitive twinning; however, instead of occurring around a rotational axis, polysynthetic twinning occurs along parallel planes, usually on a microscopic scale. Crystal habit refers to the overall shape of crystal. Several terms are used to describe this property. Common habits include acicular, which describes needlelike crystals as in natrolite , bladed, dendritic (tree-pattern, common in native copper ), equant, which

12614-568: The previous definition of a mineral to classify "element or compound, amorphous or crystalline, formed through biogeochemical processes," as a mineral. Recent advances in high-resolution genetics and X-ray absorption spectroscopy are providing revelations on the biogeochemical relations between microorganisms and minerals that may shed new light on this question. For example, the IMA-commissioned "Working Group on Environmental Mineralogy and Geochemistry " deals with minerals in

12733-503: The sea, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These sources are either mined directly, producing rock salt, or are extracted by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, purification was achieved in shallow open pans that were heated to accelerate evaporation. Vacuum -based methods are also employed. The raw salt

12852-485: The second aluminium is in six-fold coordination; its chemical formula can be expressed as Al Al SiO 5 , to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (Al Al SiO 5 ) and sillimanite has it in four-fold coordination (Al Al SiO 5 ). Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties; diamond

12971-727: The spread of civilization, salt became one of the world's main trading commodities. It was of high value to the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and other peoples of antiquity. In the Middle East, salt was used to seal an agreement ceremonially, and the ancient Hebrews made a " covenant of salt " with God and sprinkled salt on their offerings to show their trust in him. An ancient practice in time of war

13090-490: The storage of natural gas. Provadia is an important hub on both the Druzhba Gas Pipeline and as of 2015 abandoned South Stream . Other industrial facilities include a modern biodiesel installation, a sunflower oil mill, a heavy earth-mover repair plant, shipbuilding machinery and textile factories. The town has a certain potential as a spa centre; its saline mineral water is allegedly similar in composition to

13209-491: The surface of Xiechi Lake near Yuncheng in Shanxi , China, dates back to at least 6000 BC, making it one of the oldest verifiable saltworks. There is more salt in animal tissues, such as meat, blood, and milk, than in plant tissues. Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding mainly on cereals and vegetable matter, need to supplement their diet with salt. With

13328-623: The table, salt is present in many processed foods. Sodium is an essential element for human health via its role as an electrolyte and osmotic solute . However, excessive salt consumption increases the risk of cardiovascular diseases such as hypertension . Such health effects of salt have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The World Health Organization recommends that adults consume less than 2,000 mg of sodium, equivalent to 5 grams of salt, per day. All through history,

13447-455: The taste perception of food, including otherwise unpalatable food. Salting , brining , and pickling are ancient and important methods of food preservation . Some of the earliest evidence of salt processing dates to around 6000 BC, when people living in the area of present-day Romania boiled spring water to extract salts; a salt works in China dates to approximately the same period. Salt

13566-538: The time of Brahmanic sacrifices, in Hittite rituals and during festivals held by Semites and Greeks at the time of the new moon , salt was thrown into a fire where it produced crackling noises. The ancient Egyptians, Greeks and Romans invoked their gods with offerings of salt and water and some people think this to be the origin of Holy Water in the Christian faith. In Judaism , it is recommended to have either

13685-439: The twinning is controlled by the mineral's symmetry. As a result, there are several types of twins, including contact twins, reticulated twins, geniculated twins, penetration twins, cyclic twins, and polysynthetic twins. Contact, or simple twins, consist of two crystals joined at a plane; this type of twinning is common in spinel. Reticulated twins, common in rutile, are interlocking crystals resembling netting. Geniculated twins have

13804-472: The two dominant systems are the Dana classification and the Strunz classification. Silicate minerals comprise approximately 90% of the Earth's crust . Other important mineral groups include the native elements , sulfides , oxides , halides , carbonates , sulfates , and phosphates . The International Mineralogical Association has established the following requirements for a substance to be considered

13923-555: Was salting the earth : scattering salt around in a defeated city to prevent plant growth. The Bible tells the story of King Abimelech who was ordered by God to do this at Shechem , and various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War (146 BC). Salt may have been used for barter in connection with

14042-460: Was not finally abolished until 1946. In 1930, Mahatma Gandhi led a crowd of 100,000 protestors on the "Dandi March" or " Salt Satyagraha ", during which they made their own salt from the sea as a demonstration of their opposition to the colonial salt tax . This act of civil disobedience inspired numerous Indians and transformed the Indian independence movement into a national struggle. Salt

14161-482: Was prized by the ancient Hebrews , Greeks , Romans , Byzantines , Hittites , Egyptians , and Indians . Salt became an important article of trade and was transported by boat across the Mediterranean Sea , along specially built salt roads , and across the Sahara on camel caravans . The scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. Salt

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