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56-448: Onekaka Iron and Steel was first floated in 1921 with the works becoming operational in 1924 and only ceasing operation in 1935. The ironworks used the limonite ore from nearby to make iron. To smelt the iron, coal and limestone were also necessary and both limestone and the limonite were mined from the hills behind the works and ferried to the works 2.4 km away, in buckets via an aerial ropeway. Coal had originally been planned to come from

112-930: A grain boundary . Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way. Mosaicity is a spread of crystal plane orientations. A mosaic crystal consists of smaller crystalline units that are somewhat misaligned with respect to each other. In general, solids can be held together by various types of chemical bonds , such as metallic bonds , ionic bonds , covalent bonds , van der Waals bonds , and others. None of these are necessarily crystalline or non-crystalline. However, there are some general trends as follows: Metals crystallize rapidly and are almost always polycrystalline, though there are exceptions like amorphous metal and single-crystal metals. The latter are grown synthetically, for example, fighter-jet turbines are typically made by first growing

168-515: A molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state. Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins. Evaporites such as halite , gypsum and some limestones have been deposited from aqueous solution, mostly owing to evaporation in arid climates. Water-based ice in

224-619: A molten fluid, or by crystallization out of a solution. Some ionic compounds can be very hard, such as oxides like aluminium oxide found in many gemstones such as ruby and synthetic sapphire . Covalently bonded solids (sometimes called covalent network solids ) are typically formed from one or more non-metals, such as carbon or silicon and oxygen, and are often very hard, rigid, and brittle. These are also very common, notable examples being diamond and quartz respectively. Weak van der Waals forces also help hold together certain crystals, such as crystalline molecular solids , as well as

280-416: A "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure . A crystal is a solid where the atoms form a periodic arrangement. ( Quasicrystals are an exception, see below ). Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In

336-430: A fibrous or microcrystalline structure, and limonite often occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, botryoidal , reniform or stalactitic. Because of its amorphous nature, and occurrence in hydrated areas limonite often presents as a clay or mudstone. However, there are limonite pseudomorphs after other minerals such as pyrite . This means that chemical weathering transforms

392-555: A fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. As of 1999 , the world's largest known naturally occurring crystal is a crystal of beryl from Malakialina, Madagascar , 18 m (59 ft) long and 3.5 m (11 ft) in diameter, and weighing 380,000 kg (840,000 lb). Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock . The vast majority of igneous rocks are formed from molten magma and

448-423: A highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape , consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography . The process of crystal formation via mechanisms of crystal growth

504-608: A perfect, exactly repeating pattern. However, in reality, most crystalline materials have a variety of crystallographic defects : places where the crystal's pattern is interrupted. The types and structures of these defects may have a profound effect on the properties of the materials. A few examples of crystallographic defects include vacancy defects (an empty space where an atom should fit), interstitial defects (an extra atom squeezed in where it does not fit), and dislocations (see figure at right). Dislocations are especially important in materials science , because they help determine

560-434: A single crystal of titanium alloy, increasing its strength and melting point over polycrystalline titanium. A small piece of metal may naturally form into a single crystal, such as Type 2 telluric iron , but larger pieces generally do not unless extremely slow cooling occurs. For example, iron meteorites are often composed of single crystal, or many large crystals that may be several meters in size, due to very slow cooling in

616-404: A single mineral, limonite is now recognized as a field term for a mixture of related hydrated iron oxide minerals, among them goethite , lepidocrocite , akaganeite , and jarosite . Determination of the precise mineral composition is practical only with X-ray diffraction techniques. Individual minerals in limonite may form crystals , but limonite does not, although specimens may show

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672-721: A single solid. Polycrystals include most metals , rocks, ceramics , and ice . A third category of solids is amorphous solids , where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass , wax , and many plastics . Despite the name, lead crystal, crystal glass , and related products are not crystals, but rather types of glass, i.e. amorphous solids. Crystals, or crystalline solids, are often used in pseudoscientific practices such as crystal therapy , and, along with gemstones , are sometimes associated with spellwork in Wiccan beliefs and related religious movements. The scientific definition of

728-435: A wide range of properties. Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form. Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. (More rarely, crystals may be deposited directly from gas; see: epitaxy and frost .) Crystallization is a complex and extensively-studied field, because depending on

784-445: Is a noncrystalline form. Polymorphs, despite having the same atoms, may have very different properties. For example, diamond is the hardest substance known, while graphite is so soft that it is used as a lubricant. Chocolate can form six different types of crystals, but only one has the suitable hardness and melting point for candy bars and confections. Polymorphism in steel is responsible for its ability to be heat treated , giving it

840-490: Is called crystallization or solidification . The word crystal derives from the Ancient Greek word κρύσταλλος ( krustallos ), meaning both " ice " and " rock crystal ", from κρύος ( kruos ), "icy cold, frost". Examples of large crystals include snowflakes , diamonds , and table salt . Most inorganic solids are not crystals but polycrystals , i.e. many microscopic crystals fused together into

896-580: Is impossible for an ordinary periodic crystal (see crystallographic restriction theorem ). The International Union of Crystallography has redefined the term "crystal" to include both ordinary periodic crystals and quasicrystals ("any solid having an essentially discrete diffraction diagram" ). Quasicrystals, first discovered in 1982, are quite rare in practice. Only about 100 solids are known to form quasicrystals, compared to about 400,000 periodic crystals known in 2004. The 2011 Nobel Prize in Chemistry

952-483: Is its visible external shape. This is determined by the crystal structure (which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed. By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock . Crystals found in rocks typically range in size from

1008-473: Is mechanically very strong, the sheets are rather loosely bound to each other. Therefore, the mechanical strength of the material is quite different depending on the direction of stress. Not all crystals have all of these properties. Conversely, these properties are not quite exclusive to crystals. They can appear in glasses or polycrystals that have been made anisotropic by working or stress —for example, stress-induced birefringence . Crystallography

1064-435: Is named for the Ancient Greek word λειμών ( leimṓn [leː.mɔ̌ːn] ), meaning " wet meadow ", or λίμνη ( límnē [lím.nɛː] ), meaning "marshy lake", as an allusion to its occurrence as bog iron ore in meadows and marshes . In its brown form, it is sometimes called brown hematite or brown iron ore . Limonite is relatively dense with a specific gravity varying from 2.7 to 4.3. It

1120-410: Is often the major iron component in lateritic soils , and limonite laterite ores are a source of nickel and potentially cobalt and other valuable metals, present as trace elements. It is often deposited in run-off streams from mining operations. Nickel-rich limonite ores represent the largest reserves of nickel. Such minerals are classified as lateritic nickel ore deposits . One of the first uses

1176-424: Is the type of impurities present in a corundum crystal. In semiconductors , a special type of impurity, called a dopant , drastically changes the crystal's electrical properties. Semiconductor devices , such as transistors , are made possible largely by putting different semiconductor dopants into different places, in specific patterns. Twinning is a phenomenon somewhere between a crystallographic defect and

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1232-537: Is usually medium to dark yellowish brown in color. The streak of limonite on an unglazed porcelain plate is always yellowish brown, a character which distinguishes it from hematite with a red streak, or from magnetite with a black streak. The hardness is quite variable, ranging from 1 to 5. In thin section it appears as red, yellow, or brown and has a high index of refraction, 2.0–2.4. Limonite minerals are strongly birefringent, but grain sizes are usually too small for this to be detectable. Although originally defined as

1288-554: The Dahlonega gold belt in Lumpkin County, Georgia gold was mined from limonite-rich lateritic or saprolite soil. As saprolite deposits have been exhausted in many mining sites, limonite has become the most prominent source of nickel for use in energy dense batteries. Crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms , molecules , or ions ) are arranged in

1344-564: The Mataura field, but was eventually sourced from Westport . When the industrial use of the iron ore in nearby Parapara was first considered in the early 1900s, it was envisaged to build a wharf north of Tukurua Point. The Parapara iron ore had since the 1870s been used for making red paint, with a tram eventually connecting to a wharf. Skilton's wharf on the Onekaka Inlet was used to deliver building materials and equipment to build

1400-447: The mechanical strength of materials . Another common type of crystallographic defect is an impurity , meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of diamond would only contain carbon atoms, but a real crystal might perhaps contain a few boron atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between ruby and sapphire

1456-429: The air ( ice fog ) more often grow from a supersaturated gaseous-solution of water vapor and air, when the temperature of the air drops below its dew point , without passing through a liquid state. Another unusual property of water is that it expands rather than contracts when it crystallizes. Many living organisms are able to produce crystals grown from an aqueous solution , for example calcite and aragonite in

1512-510: The case of most molluscs or hydroxylapatite in the case of bones and teeth in vertebrates . The same group of atoms can often solidify in many different ways. Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water ice is ordinarily found in the hexagonal form Ice I h , but can also exist as the cubic Ice I c , the rhombohedral ice II , and many other forms. The different polymorphs are usually called different phases . In addition,

1568-404: The conditions, a single fluid can solidify into many different possible forms. It can form a single crystal , perhaps with various possible phases , stoichiometries , impurities, defects , and habits . Or, it can form a polycrystal , with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which

1624-409: The crystal can shrink or stretch it. Another is birefringence , where a double image appears when looking through a crystal. Moreover, various properties of a crystal, including electrical conductivity , electrical permittivity , and Young's modulus , may be different in different directions in a crystal. For example, graphite crystals consist of a stack of sheets, and although each individual sheet

1680-411: The crystal is one grain in a polycrystalline solid. The flat faces (also called facets ) of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal : they are planes of relatively low Miller index . This occurs because some surface orientations are more stable than others (lower surface energy ). As a crystal grows, new atoms attach easily to

1736-532: The crystals may form hexagons, such as ordinary water ice ). Crystals are commonly recognized, macroscopically, by their shape, consisting of flat faces with sharp angles. These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see. Euhedral crystals are those that have obvious, well-formed flat faces. Anhedral crystals do not, usually because

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1792-548: The crystals of pyrite into limonite by hydrating the molecules, but the external shape of the pyrite crystal remains. Limonite pseudomorphs have also been formed from other iron oxides, hematite and magnetite; from the carbonate siderite and from iron rich silicates such as almandine garnets . Limonite usually forms from the hydration of hematite and magnetite, from the oxidation and hydration of iron rich sulfide minerals, and chemical weathering of other iron rich minerals such as olivine , pyroxene , amphibole , and biotite . It

1848-606: The degree of crystallization depends primarily on the conditions under which they solidified. Such rocks as granite , which have cooled very slowly and under great pressures, have completely crystallized; but many kinds of lava were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or glassy matter is common. Other crystalline rocks, the metamorphic rocks such as marbles , mica-schists and quartzites , are recrystallized. This means that they were at first fragmental rocks like limestone , shale and sandstone and have never been in

1904-453: The eight faces of the octahedron belong to another crystallographic form reflecting a different symmetry of the isometric system. A crystallographic form is described by placing the Miller indices of one of its faces within brackets. For example, the octahedral form is written as {111}, and the other faces in the form are implied by the symmetry of the crystal. Forms may be closed, meaning that

1960-710: The final block of ice, each of the small crystals (called " crystallites " or "grains") is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries . Most macroscopic inorganic solids are polycrystalline, including almost all metals , ceramics , ice , rocks , etc. Solids that are neither crystalline nor polycrystalline, such as glass , are called amorphous solids , also called glassy , vitreous, or noncrystalline. These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably,

2016-531: The fluid is being solidified, such as the chemistry of the fluid, the ambient pressure , the temperature , and the speed with which all these parameters are changing. Specific industrial techniques to produce large single crystals (called boules ) include the Czochralski process and the Bridgman technique . Other less exotic methods of crystallization may be used, depending on the physical properties of

2072-415: The form can completely enclose a volume of space, or open, meaning that it cannot. The cubic and octahedral forms are examples of closed forms. All the forms of the isometric system are closed, while all the forms of the monoclinic and triclinic crystal systems are open. A crystal's faces may all belong to the same closed form, or they may be a combination of multiple open or closed forms. A crystal's habit

2128-402: The form of snow , sea ice , and glaciers are common crystalline/polycrystalline structures on Earth and other planets. A single snowflake is a single crystal or a collection of crystals, while an ice cube is a polycrystal . Ice crystals may form from cooling liquid water below its freezing point, such as ice cubes or a frozen lake. Frost , snowflakes, or small ice crystals suspended in

2184-458: The interlayer bonding in graphite . Substances such as fats , lipids and wax form molecular bonds because the large molecules do not pack as tightly as atomic bonds. This leads to crystals that are much softer and more easily pulled apart or broken. Common examples include chocolates, candles, or viruses. Water ice and dry ice are examples of other materials with molecular bonding. Polymer materials generally will form crystalline regions, but

2240-493: The ironworks in Onekaka, and take away the finished product. However, in 1923 the company was granted permission to build a pier 365 metres long from Onekaka Beach to deep water. A tramline was built in 1924, running 2.6 kilometres from the wharf to the ironworks. This crossed the inlet on raised trestles, and passed under the highway. In 1928–29, a hydro-electric scheme was built to power the pipe-making plant. The blast furnace

2296-471: The lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous. A quasicrystal consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in x-ray diffraction , and the ability to form shapes with smooth, flat faces. Quasicrystals are most famous for their ability to show five-fold symmetry, which

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2352-413: The process of forming a glass does not release the latent heat of fusion , but forming a crystal does. A crystal structure (an arrangement of atoms in a crystal) is characterized by its unit cell , a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal. The symmetry of a crystal is constrained by

2408-432: The requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries (230 is commonly cited, but this treats chiral equivalents as separate entities), called crystallographic space groups . These are grouped into 7 crystal systems , such as cubic crystal system (where the crystals may form cubes or rectangular boxes, such as halite shown at right) or hexagonal crystal system (where

2464-513: The resulting soils. Limonite was one of the earliest materials used as a pigment by humans, and can be seen in Neolithic cave paintings and pictographs . While the first iron ore was likely meteoric iron , and hematite was far easier to smelt , in Africa, where the first evidence of iron metallurgy occurs, limonite is the most prevalent iron ore. Before smelting, as the ore was heated and

2520-423: The rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.) One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer

2576-444: The same atoms may be able to form noncrystalline phases . For example, water can also form amorphous ice , while SiO 2 can form both fused silica (an amorphous glass) and quartz (a crystal). Likewise, if a substance can form crystals, it can also form polycrystals. For pure chemical elements, polymorphism is known as allotropy . For example, diamond and graphite are two crystalline forms of carbon , while amorphous carbon

2632-744: The substance, including hydrothermal synthesis , sublimation , or simply solvent-based crystallization . Large single crystals can be created by geological processes. For example, selenite crystals in excess of 10  m are found in the Cave of the Crystals in Naica, Mexico. For more details on geological crystal formation, see above . Crystals can also be formed by biological processes, see above . Conversely, some organisms have special techniques to prevent crystallization from occurring, such as antifreeze proteins . An ideal crystal has every atom in

2688-429: The underlying crystal symmetry . A crystal's crystallographic forms are sets of possible faces of the crystal that are related by one of the symmetries of the crystal. For example, crystals of galena often take the shape of cubes, and the six faces of the cube belong to a crystallographic form that displays one of the symmetries of the isometric crystal system . Galena also sometimes crystallizes as octahedrons, and

2744-620: The vacuum of space. The slow cooling may allow the precipitation of a separate phase within the crystal lattice, which form at specific angles determined by the lattice, called Widmanstatten patterns . Ionic compounds typically form when a metal reacts with a non-metal, such as sodium with chlorine. These often form substances called salts, such as sodium chloride (table salt) or potassium nitrate ( saltpeter ), with crystals that are often brittle and cleave relatively easily. Ionic materials are usually crystalline or polycrystalline. In practice, large salt crystals can be created by solidification of

2800-466: The water driven off, more and more of the limonite was converted to hematite. The ore was then pounded as it was heated above 1250 °C, at which temperature the metallic iron begins sticking together and non-metallic impurities are thrown off as sparks. Complex systems developed, notably in Tanzania, to process limonite. Nonetheless, hematite and magnetite remained the ores of choice when smelting

2856-563: The works ceased in 1954. Onekaka Ironworks Wharf and Tramline Piles have been declared part of New Zealand's cultural heritage, which has "significance as a poignant physical link to an ambitious iron mining and smelting scheme". [REDACTED] Media related to Onekakā Ironworks at Wikimedia Commons [REDACTED] Media related to Onekaka Wharf at Wikimedia Commons Images from the Alexander Turnbull Library Limonite Limonite

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2912-420: Was able to produce 10,000 tons of iron per year, outrunning local demand, and produced over 81,000 tons of iron between 1922 and 1935. However, the plant could not compete with overseas iron and by 1930 the market for iron pipes had also collapsed. By 1931, the company was in receivership, closing in 1935. in 1938, the government acquired the ironworks and there were proposals to revive them, but efforts to revive

2968-529: Was as a pigment . The yellow form produced yellow ochre for which Cyprus was famous, while the darker forms produced more earthy tones. Roasting the limonite changed it partially to hematite, producing red ochres, burnt umbers and siennas . Bog iron ore and limonite mudstones are mined as a source of iron. Iron caps or gossans of siliceous iron oxide typically form as the result of intensive oxidation of sulfide ore deposits. These gossans were used by prospectors as guides to buried ore. Limonite

3024-400: Was awarded to Dan Shechtman for the discovery of quasicrystals. Crystals can have certain special electrical, optical, and mechanical properties that glass and polycrystals normally cannot. These properties are related to the anisotropy of the crystal, i.e. the lack of rotational symmetry in its atomic arrangement. One such property is the piezoelectric effect , where a voltage across

3080-850: Was by bloomeries , and it was only with the development of blast furnaces in the 1st century BCE in China and about 1150 CE in Europe, that the brown iron ore of limonite could be used to best advantage. Bog iron ore and limonite were mined in the US, but this ended with the development of advanced mining techniques. Goldbearing limonite gossans were productively mined in the Shasta County, California mining district. Similar deposits were mined near Rio Tinto in Spain and Mount Morgan in Australia . In

3136-401: Was mined for its ancillary gold content. The oxidation of sulfide deposits which contained gold , often resulted in the concentration of gold in the iron oxide and quartz of the gossans. The gold of the primary veins was concentrated into the limonites of the deeply weathered rocks. In another example the deeply weathered iron formations of Brazil served to concentrate gold with the limonite of

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