Ferroan calcite-galena (Dalnegorsk Skarn Deposit, Late Cretaceous, 70-90 Ma; 2nd Sovietsky Mine, Dalnegorsk, Russia) 3 : 無料・フリー素材/写真
Ferroan calcite-galena (Dalnegorsk Skarn Deposit, Late Cretaceous, 70-90 Ma; 2nd Sovietsky Mine, Dalnegorsk, Russia) 3 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Ferroan calcite-galena from Russia.Dark yellow = calciteSilvery-black = galenaA mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.--------------The carbonate minerals all contain one or more carbonate (CO3-2) anions.Calcite is a common mineral. It is calcium carbonate (CaCO3). It has a nonmetallic luster, commonly clearish to whitish to yellowish to grayish in color, is moderately soft (H≡3), moderately light-weight, has hexagonal crystals, and rhombohedral cleavage (three cleavage planes at 75º & 105º angles - cleavage pieces look like lopsided boxes). The easiest way to identify calcite is to drop acid on it - it easily bubbles (effervesces) in acid. The bubbles are carbon dioxide gas. If the acid is dilute hydrochloric acid, the chemical reaction is: 2HCl(aq) + CaCO3(s) -->> CO2(g)↑ + H2O(l) + CaCl2(aq) The most important & voluminous calcitic rocks in the world are limestone (sedimentary), marble (metamorphic), carbonatite (igneous), and travertine (speleothem, or "cave formations", and many hotspring deposits). Quite a few hydrothermal veins in the world are calcitic or have calcite as a principal component.The dark yellowish coloration present in the calcite seen here is from significant iron impurity.--------------The sulfide minerals contain one or more sulfide anions (S-2). The sulfides are usually considered together with the arsenide minerals, the sulfarsenide minerals, and the telluride minerals. Many sulfides are economically significant, as they occur commonly in ores. The metals that combine with S-2 are mainly Fe, Cu, Ni, Ag, etc. Most sulfides have a metallic luster, are moderately soft, and are noticeably heavy for their size. These minerals will not form in the presence of free oxygen. Under an oxygen-rich atmosphere, sulfide minerals tend to chemically weather to various oxide and hydroxide minerals.Galena is a lead sulfide mineral (PbS). It has a metallic luster, silvery-gray color, cubic crystals, cubic cleavage, is moderately soft, and has a very high specific gravity (it's very heavy for its size). Galena is the most important lead ore mineral. It's principally found in hydrothermal vein systems and in Mississippi Valley-type deposits. Silver (Ag) can fall into the lead position as an impurity, sometimes in relatively high proportions. This results in argentiferous galena, (Pb,Ag)S. Historically, lead from galena has been used as a gasoline additive, a paint ingredient, and for making bullets. Lead is also used to make various metal products, batteries, and radiation shielding.--------------This specimen comes from a polymetallic sulfide ore body at the famous Dalnegorsk skarn deposit in far-eastern Russia. The deposit consists of mineral-filled solution cavities in Triassic limestones that have been intruded by Late Cretaceous granodiorites. The skarn zone itself has been intruded by 64 Ma granite.Locality: 2nd Sovietsky Mine (Second Soviet Mine), Dalnegorsk, Primorskiy Kray, far-eastern Russia--------------Photo gallery of ferroan calcite:www.mindat.org/gallery.php?min=10299--------------Photo gallery of galena:www.mindat.org/gallery.php?min=1641 |
| 撮影日 | 2025-04-26 16:38:26 |
| 撮影者 | James St. John |
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