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- align=center bgcolor="#9966FF" | Пирит | - align=center |
Сросток кристаллов пирита
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Euhedral cubic pyrite crystals
- align=center bgcolor="#9966FF" | General | - | Category | Mineral | - | Chemical formula | iron disulfide (FeS2) | - align="center" bgcolor="#9966FF" | Identification | - | Colour | Pale, dull gold | - | Crystal habit | Cubic, faces may be striated, but also frequently octahedral and pyritohedron. Often inter-grown, massive, radiated, granular, globular and stalactitic. | - | Crystal system | Isometric; bar 3 2/m | - | Melting Point | 1,177-1,188°C * | - | Cleavage | Poor | - | Fracture | Very uneven, sometimes conchoidal | - | Mohs Scale hardness | 6 - 6.5 | - | Luster | Metallic, glistening | - | Refractive index | Opaque | - | Streak | Greenish-black to brownish-black | - | Specific gravity | 4.95 - 5.10 | - | Fusibility | 2.5-3 | - | Solubility | insoluble in water | - | Magnetism | paramagnetic | - |
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Пирит (, буквально — камень высекающий огонь) — минерал, сульфид железа химического состава FeS2 (46,6 % Fe, 53,4 % S). Нередки примеси Со, Ni, As, Cu, Au, Se и других веществ.
Так же известен под названиями: серный колчедан, железный колчедан.
Греческое название камень, высекающий огонь связано со свойством пирита давать искры при ударе.
Пирит кристаллизуется в кубической сингонии, образуя кубические, пентагондодекаэдрические и реже октаэдрические кристаллы. Но распространён чаще всего в виде сплошных зернистых масс. Цвет светлый, латунно-жёлтый. Имеет металлический блеск.
Твердость по шкале Мооса 6…6,5 (уменьшается при повышении содержания Ni); плотность 4900—5200 кг/м3.
Пирит — один из самых распространенных сульфидов. Большие его залежи сосредоточены в месторождениях гидротермального происхождения, колчеданных залежах, осадочных и метаморфических породах. Кроме того пирит в небольших количествах образуется в магматических процессах. В осадочных породах пирит образуется закрытых морских бассейнах подобных Черному Морю, в результате осаждения сероводорода.
Пирит является сырьём для получения серной кислоты, серы и Железного купороса, но последнее время редко используется для этих целей. В огромных объемах он извлекается при разработке гидротермальных месторождений меди, свинца, цинка, олова и других цветных металлов. Но переработка пирита в полезные компоненты обычно оказывается экономически не выгодной, и его отправляют в отвалы.
В России месторождения пирита расположены на Урале (Дегтярское, Калатинское и др.), на Алтае, Закавказье и других районах. За рубежом — в Казахстане, Норвегии, Испании (Рио-Тинто), Италии, на острове Кипр, в США, Канаде, Японии.
results from the action of Thiobacillus bacteria, which generate their energy by using oxygen to oxidize ferrous iron (Fe2+) to ferric iron (Fe3+). The ferric iron in turn reacts with pyrite to produce ferrous iron and sulfuric acid. The ferrous iron is then available for oxidation by the bacteria; this cycle can continue until the pyrite is exhausted.
Pyrite is used for the production of sulfur dioxide, e.g. for the paper industry, and in the manufacture of sulfuric acid, though such applications are declining in importance.
Pyrites can show negative resistance and have experimentally been used in oscillator circuits as radio detectors *.
The name pyrite is from the Greek word "Pyr" meaning "fire". This is likely due to the sparks that result when pyrite is struck against steel. This capacity made it popular for use in early firearms such as the wheellock.
In her historical fiction book The Valley of Horses, Jean Auel's heroine Ayla is described as inventing a new method of creating fire by striking a pyrite-like material against flint.
Pyrite and marcasite
Pyrite is often confused with the mineral marcasite, a name derived from the Arabic word for pyrite, due to their similar characteristics. Marcasite is a polymorph of pyrite, which means it has the same formula as pyrite but a different structure and, therefore, different symmetry and crystal shapes. The formal oxidation states are, however, the same as in pyrite because again the sulfur atoms occur in persulfide-like pairs. Marcasite/pyrite is probably the most famous polymorph pair next to the diamond/graphite pair.
Marcasite is metastable relative to pyrite and will slowly be changed to pyrite if heated or given enough time. Marcasite is relatively rare, but may be locally abundant in some types of ore deposits, such as Mississippi Valley-type Pb-Zn deposits. Marcasite appears to form only from aqueous solutions.
Pyrite is often used in jewellery (jewelry) such as necklaces and bracelets, but although the two are similar, marcasite cannot be used in jewellery as it has a tendency to crumble into powder. Adding to the confusion between marcasite and pyrite is the use of the word marcasite as a jewellery trade name. The term is applied to small polished and faceted stones that are inlaid in sterling silver, but even though they are called marcasite, they are actually pyrite.
Formal oxidation states for pyrite, marcasite, and arsenopyrite
From the perspective of classical inorganic chemistry, which assigns formal oxidation states to each atom, pyrite is probably best described as Fe2+S22-. This formalism recognizes that the sulfur atoms in pyrite occur in pairs with clear S-S bonds. These persulfide units can be viewed as derived from hydrogen persulfide, H2S2. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast, molybdenite, MoS2, features isolated sulfide (S2-) centers. Consequently, the oxidation state of molybdenum is Mo4+, or Mo(IV). The mineral arsenopyrite has the formula FeAsS. Whereas pyrite has S2 subunits, arsenopyrite has AsS units, formally derived from deprotonation of H2AsSH. Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe3+AsS3-. Of course these formalisms ignore covalency, which is strongly implied by the semi-conducting behavior of this family of inorganic solids.
Sulfide minerals | Iron minerals
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Ссылки
- Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York, p 285-286, ISBN 0471805807
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Pirita | Pyrit | Pyrit | Pyrite | Pirita | Rikkikiisu | Pyrite | פיריט | Pirite | 黄鉄鉱 | Piritas | Pyriet | Svovelkis | Piryt | Pirita | Pyrit | Svavelkis | پىرىت | 黄铁矿
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