Hematite spelled as haematite, is the mineral form of iron oxide, one of several iron oxides. It is the oldest known iron oxide mineral that has formed on Earth, is widespread in rocks and soils. Hematite crystallizes in the rhombohedral lattice system, it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above 950 °C. Hematite is colored brown to reddish brown, or red, it is mined as the main ore of iron. Varieties include kidney ore, iron rose and specularite. While the forms of hematite vary, they all have a rust-red streak. Hematite is much more brittle. Maghemite is a hematite- and magnetite-related oxide mineral. Huge deposits of hematite are found in banded iron formations. Gray hematite is found in places that can have still standing water or mineral hot springs, such as those in Yellowstone National Park in North America; the mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water.
Hematite can occur without water, however as the result of volcanic activity. Clay-sized hematite crystals can occur as a secondary mineral formed by weathering processes in soil, along with other iron oxides or oxyhydroxides such as goethite, is responsible for the red color of many tropical, ancient, or otherwise weathered soils; the name hematite is derived from the Greek word for blood αἷμα haima, due to the red coloration found in some varieties of hematite. The color of hematite lends itself to use as a pigment; the English name of the stone is derived from Middle French: Hématite Pierre, imported from Latin: Lapis Hæmatites around the 15th century, which originated from Ancient Greek: αἱματίτης λίθος. Ochre is a clay, colored by varying amounts of hematite, varying between 20% and 70%. Red ochre contains unhydrated hematite; the principal use of ochre is for tinting with a permanent color. The red chalk writing of this mineral was one of the earliest in the history of humans; the powdery mineral was first used 164,000 years ago by the Pinnacle-Point man for social purposes.
Hematite residues are found in graves from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary red chalk mines have been found that are from 5000 BC, belonging to the Linear Pottery culture at the Upper Rhine. Rich deposits of hematite have been found on the island of Elba that have been mined since the time of the Etruscans. Hematite is an antiferromagnetic material below the Morin transition at 250 K, a canted antiferromagnet or weakly ferromagnetic above the Morin transition and below its Néel temperature at 948 K, above which it is paramagnetic; the magnetic structure of a-hematite was the subject of considerable discussion and debate in the 1950s because it appeared to be ferromagnetic with a Curie temperature of around 1000 K, but with an tiny magnetic moment. Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment, it was shown that the system is antiferromagnetic, but that the low symmetry of the cation sites allows spin–orbit coupling to cause canting of the moments when they are in the plane perpendicular to the c axis.
The disappearance of the moment with a decrease in temperature at 260 K is caused by a change in the anisotropy which causes the moments to align along the c axis. In this configuration, spin canting does not reduce the energy; the magnetic properties of bulk hematite differ from their nanoscale counterparts. For example, the Morin transition temperature of hematite decreases with a decrease in the particle size; the suppression of this transition has been observed in some of the hematite nanoparticles, the presence of impurities, water molecules and defects in the crystals were attributed to the absence of a Morin transition. Hematite is part of a complex solid solution oxyhydroxide system having various contents of water, hydroxyl groups and vacancy substitutions that affect the mineral's magnetic and crystal chemical properties. Two other end-members are referred to as hydrohematite. Enhanced magnetic coercivities for hematite have been achieved by dry-heating a 2-line ferrihydrite precursor prepared from solution.
Hematite exhibited temperature-dependent magnetic coercivity values ranging from 289 to 5,027 Oe. The origin of these high coercivity values has been interpreted as a consequence of the subparticle structure induced by the different particle and crystallite size growth rates at increasing annealing temperature; these differences in the growth rates are translated into a progressive development of a subparticle structure at the nanoscale. At lower temperatures, single particles crystallize however. Hematite is present in the waste tailings of iron mines. A developed process, uses magnets to glean waste hematite from old mine tailings in Minnesota's vast Mesabi Range iron district. Falu red is a pigment used in traditional Swedish house paints, it was made from tailings of the Falu mine. The spectral signature of hematite was seen on the planet Mars by the infrared spectrometer on the NASA Mars Global Surveyor and 2001 Mars Odyssey spacecraft in orbit around Mars; the mineral was seen in abundance at two sites on the planet, the Terra Meridiani site, near the Martian equator at 0° longitude, the Aram
A winding engine is a stationary engine used to control a cable, for example to power a mining hoist at a pit head. Electric hoist controllers have replaced proper winding engines in modern mining, but use electric motors that are traditionally referred to as winding engines. Early winding engines were hand, or more horse powered; the first powered winding engines were stationary steam engines. The demand for winding engines was one factor that drove James Watt to develop his rotative beam engine, with its ability to continuously turn a winding drum, rather than the early reciprocating beam engines that were only useful for working pumps, they differ from most other stationary steam engines in that, like a steam locomotive, they need to be able to stop and reverse. This requires more complex valve gear and other controls than are needed on engines used in mills or to drive pumps
Mohs scale of mineral hardness
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative; the method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is relevant for field geologists, who use the scale to identify minerals using scratch kits; the Mohs scale hardness of minerals can be found in reference sheets. Mohs hardness is useful in milling, it allows assessment of.
The scale is used at electronic manufacturers for testing the resilience of flat panel display components. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly; the samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals; as the hardest known occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5. "Scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye. Materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number.
While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number. The Mohs scale is a purely ordinal scale. For example, corundum is twice as hard as topaz; the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale; the table below incorporates additional substances that may fall between levels: Comparison between hardness and hardness: Mohs hardness of elements is taken from G. V. Samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA, 1968. Cordua, William S. "The Hardness of Minerals and Rocks". Lapidary Digest, c. 1990
In the field of mineralogy, fracture is the texture and shape of a rock's surface formed when a mineral is fractured. Minerals have a distinctive fracture, making it a principal feature used in their identification. Fracture differs from cleavage in that the latter involves clean splitting along the cleavage planes of the mineral's crystal structure, as opposed to more general breakage. All minerals exhibit fracture, but when strong cleavage is present, it can be difficult to see. Conchoidal fracture breakage that resembles the concentric ripples of a mussel shell, it occurs in amorphous or fine-grained minerals such as flint, opal or obsidian, but may occur in crystalline minerals such as quartz. Subconchoidal fracture is similar to with less significant curvature. Earthy fracture is reminiscent of freshly broken soil, it is seen in soft, loosely bound minerals, such as limonite and aluminite. Hackly fracture is jagged and not even, it occurs when metals are torn, so is encountered in native metals such as copper and silver.
Splintery fracture comprises sharp elongated points. It is seen in fibrous minerals such as chrysotile, but may occur in non-fibrous minerals such as kyanite. Uneven fracture is a rough one with random irregularities, it occurs in a wide range of minerals including arsenopyrite and magnetite. Rudolf Duda and Lubos Rejl: Minerals of the World http://www.galleries.com/minerals/property/fracture.htm
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation; the hydraulic flow involved is due to hydrothermal circulation. Veins are classically thought of as being the result of growth of crystals on the walls of planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, the crystal protruding into open space; this is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock several kilometers below the surface. Thus, there are two main mechanisms considered for the formation of veins: open-space filling and crack-seal growth. Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space filling to take effect, the confining pressure is considered to be below 0.5 GPa, or less than 3–5 km.
Veins formed in this way may exhibit a colloform, agate-like habit, of sequential selvages of minerals which radiate out from nucleation points on the vein walls and appear to fill up the available open space. Evidence of fluid boiling is present. Vugs and geodes are all examples of open-space filling phenomena in hydrothermal systems. Alternatively, hydraulic fracturing may create a breccia, filled with vein material; such breccia vein systems may be quite extensive, can form the shape of tabular dipping sheets, diatremes or laterally extensive mantos controlled by boundaries such as thrust faults, competent sedimentary layers, or cap rocks. When the confining pressure is too great, or when brittle-ductile rheological conditions predominate, vein formation occurs via crack-seal mechanisms. Crack-seal veins are thought to form quite during deformation by precipitation of minerals within incipient fractures; this happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained.
Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface. Veins need either hydraulic pressure in excess of hydrostatic pressure or they need open spaces or fractures, which requires a plane of extension within the rock mass. In all cases except brecciation, therefore, a vein measures the plane of extension within the rock mass, give or take a sizeable bit of error. Measurement of enough veins will statistically form a plane of principal extension. In ductilely deforming compressional regimes, this can in turn give information on the stresses active at the time of vein formation. In extensionally deforming regimes, the veins occur normal to the axis of extension. Veins are of prime importance to mineral deposits, because they are the source of mineralisation either in or proximal to the veins. Typical examples include gold lodes, as well as skarn mineralisation. Hydrofracture breccias are classic targets for ore exploration as there is plenty of fluid flow and open space to deposit ore minerals.
Ores related to hydrothermal mineralisation, which are associated with vein material, may be composed of vein material and/or the rock in which the vein is hosted. In many gold mines exploited during the gold rushes of the 19th century, vein material alone was sought as ore material. In most of today's mines, ore material is composed of the veins and some component of the wall rocks which surrounds the veins; the difference between 19th-century and 21st-century mining techniques and the type of ore sought is based on the grade of material being mined and the methods of mining which are used. Hand-mining of gold ores permitted the miners to pick out the lode quartz or reef quartz, allowing the highest-grade portions of the lodes to be worked, without dilution from the unmineralised wall rocks. Today's mining, which uses larger machinery and equipment, forces the miners to take low-grade waste rock in with the ore material, resulting in dilution of the grade. However, today's mining and assaying allows the delineation of lower-grade bulk tonnage mineralisation, within which the gold is invisible to the naked eye.
In these cases, veining is the subordinate host to mineralisation and may only be an indicator of the presence of metasomatism of the wall-rocks which contains the low-grade mineralisation. For this reason, veins within hydrothermal gold deposits are no longer the exclusive target of mining, in some cases gold mineralisation is restricted to the altered wall rocks within which barren quartz veins are hosted. Boudinage Ore genesis Shear
Galena called lead glance, is the natural mineral form of lead sulfide. It is an important source of silver. Galena is one of the most abundant and distributed sulfide minerals, it crystallizes in the cubic crystal system showing octahedral forms. It is associated with the minerals sphalerite and fluorite. Galena is the main ore of lead, used since ancient times; because of its somewhat low melting point, it was easy to liberate by smelting. It forms in low-temperature sedimentary deposits. In some deposits the galena contains about 1–2% silver, a byproduct that far outweighs the main lead ore in revenue. In these deposits significant amounts of silver occur as included silver sulfide mineral phases or as limited silver in solid solution within the galena structure; these argentiferous galenas have long been an important ore of silver. Galena deposits are found worldwide in various environments. Noted deposits include those at Freiberg in Saxony. In the United States, it occurs most notably in the Mississippi Valley type deposits of the Lead Belt in southeastern Missouri, in the Driftless Area of Illinois and Wisconsin.
Galena was a major mineral of the zinc-lead mines of the tri-state district around Joplin in southwestern Missouri and the adjoining areas of Kansas and Oklahoma. Galena is an important ore mineral in the silver mining regions of Colorado, Idaho and Montana. Of the latter, the Coeur d'Alene district of northern Idaho was most prominent. Galena is the official state mineral of the U. S. states of Wisconsin. The largest documented crystal of galena is composite cubo-octahedra from the Great Laxey Mine, Isle of Man, measuring 25 cm × 25 cm × 25 cm. Galena belongs to the octahedral sulfide group of minerals that have metal ions in octahedral positions, such as the iron sulfide pyrrhotite and the nickel arsenide niccolite; the galena group is named after its most common member, with other isometric members that include manganese bearing alabandite and niningerite. Divalent lead cations and sulfur anions form a close-packed cubic unit cell much like the mineral halite of the halide mineral group. Zinc, iron, antimony, arsenic and selenium occur in variable amounts in galena.
Selenium substitutes for sulfur in the structure constituting a solid solution series. The lead telluride mineral altaite has the same crystal structure as galena. Within the weathering or oxidation zone galena alters to cerussite. Galena exposed to acid mine drainage can be oxidized to anglesite by occurring bacteria and archaea, in a process similar to bioleaching. One of the oldest uses of galena was in the eye cosmetic kohl. In Ancient Egypt, this was applied around the eyes to reduce the glare of the desert sun and to repel flies, which were a potential source of disease. Galena is the primary ore of lead, used in making lead–acid batteries. Galena is mined for its silver content, such as at the Galena Mine in northern Idaho. Known as "potter's ore", galena is used in a green glaze applied to pottery. Galena is a semiconductor with a small band gap of about 0.4 eV, which found use in early wireless communication systems. It was used as the crystal in crystal radio receivers, in which it was used as a point-contact diode capable of rectifying alternating current to detect the radio signals.
The galena crystal was used with a sharp wire, known as a "cat's whisker" in contact with it. The operation of the radio required that the point of contact on the galena be shifted about to find a part of the crystal that acted as a rectifying diode. Making such wireless receivers was a popular home hobby in Britain and other European countries during the 1930s. Scientists associated with the investigation of the diode effect are Karl Ferdinand Braun and Jagadish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices. List of minerals Lead smelter Klein, Cornelis. Manual of Mineralogy. Wiley. Pp. 274–276. ISBN 0-471-80580-7. Case Studies in Environmental Medicine: Lead Toxicity. ToxFAQs: Lead. Mineral Information Institute entry for lead
Carbonate minerals are those minerals containing the carbonate ion, CO32−. Calcite group: trigonal Calcite CaCO3 Gaspeite CO3 Magnesite MgCO3 Otavite CdCO3 Rhodochrosite MnCO3 Siderite FeCO3 Smithsonite ZnCO3 Spherocobaltite CoCO3 Aragonite group: orthorhombic Aragonite CaCO3 Cerussite PbCO3 Strontianite SrCO3 Witherite BaCO3 Rutherfordine UO2CO3 Natrite Na2CO3 Dolomite group: trigonal Ankerite CaFe2 Dolomite CaMg2 Huntite Mg3Ca4 Minrecordite CaZn2 Barytocite BaCa2 Carbonate with hydroxide: monoclinic Azurite Cu322 Hydrocerussite Pb322 Malachite Cu2CO32 Rosasite 2CO32 Phosgenite Pb2Cl2 Hydrozincite Zn526 Aurichalcite 526 Hydromagnesite Mg542.4H2O Ikaite CaCO3·6 Lansfordite MgCO3·5 Monohydrocalcite CaCO3·H2O Natron Na2CO3·10 Zellerite Ca2·5The carbonate class in both the Dana and the Strunz classification systems include the nitrates. IMA-CNMNC proposes a new hierarchical scheme; this list uses the classification of Nickel–Strunz. Abbreviations: "*" – discredited. "?" – questionable/doubtful.
"REE" – Rare-earth element "PGE" – Platinum-group element 03. C Aluminofluorides, 06 Borates, 08 Vanadates, 09 Silicates: Neso: insular Soro: grouping Cyclo: ring Ino: chain Phyllo: sheet Tekto: three-dimensional framework Nickel–Strunz code scheme: NN. XY.##x NN: Nickel–Strunz mineral class number X: Nickel–Strunz mineral division letter Y: Nickel–Strunz mineral family letter ##x: Nickel–Strunz mineral/group number, x add-on letter 05. A Carbonates without additional anions, without H2O 05. AA Alkali carbonates: 05 Zabuyelite. AB Alkali-earth carbonates: 05 Calcite, 05 Gaspeite, 05 Magnesite, 05 Rhodochrosite, 05 Otavite, 05 Spherocobaltite, 05 Siderite, 05 Smithsonite. AC Alkali and alkali-earth carbonates: 05 Eitelite, 10 Nyerereite, 10 Natrofairchildite, 10 Zemkorite. AD With rare-earth elements: 05 Sahamalite-. B Carbonates with additional anions, without H2O 05. BA With Cu, Co, Ni, Zn, Mg, Mn: 05 Azurite, 10 Chukanovite, 10 Malachite, 10 Georgeite, 10 Pokrovskite, 10 Nullaginite, 10 Glaukosphaerite, 10 Mcguinnessite, 10 Kolwezite, 10 Rosasite, 10 Zincrosasite.
BB With alkalies, etc.: 05 Barentsite, 10 Dawsonite, 15 Tunisite, 20 Sabinaite 05. BC With alkali-earth cations: 05 Brenkite, 10 Rouvilleite, 15 Podlesnoite 05. BD With rare-earth elements: 05 Cordylite-, 05 Lukechangite-. BE With Pb, Bi: 05 Shannonite, 10 Hydrocerussite, 15 Plumbonacrite, 20 Phosgenite, 25 Bismutite, 30 Kettnerite, 35 Beyerite 05. BF With, SO4, PO4, TeO3: 05 Northupite, 05 Ferrotychite, 05 Manganotychite, 05 Tychite. C Carbonates without additional anions, with H2O 05. CA With medium-sized cations: 05 Nesquehonite, 10 Lansfordite, 15 Barringtonite, 20 Hellyerite 05. CB With large cations: 05 Thermonatrite, 10 Natron, 15 Trona, 20 Monohydrocalcite, 25 Ikaite, 30 Pirssonite, 35 Gaylussite, 40 Chalconatronite, 45 Baylissite, 50 Tuliokite 05. CC With rare-earth elements: 05 Donnayite-, 05 Mckelveyite-*, 05 Mckelveyite-, 05 Weloganite. D Carbonates with additional anions, with H2O 05. DA With medium-sized cations: 05 Dypingite, 05 Giorgiosite, 05 Hydromagnesite, 05 Widgiemoolthalite.
DB With large and medium-sized cations: 05 Alumohydrocalcite, 05 Para-alumohydrocalcite, 05 Nasledovite.