Gypsum (Naica, Chihuahua, Mexico) 1 : 無料・フリー素材/写真
Gypsum (Naica, Chihuahua, Mexico) 1 / 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 | Large gypsum crystals from Mexico. (photo of public signage at Denver Museum of Nature & Science, Denver, Colorado, USA)A 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 6000 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 sulfate minerals all have one or more sulfate anions (SO4 -2).Gypsum is a moderately common hydrous calcium sulfate mineral (CaSO4·2H2O). Gypsum has a nonmetallic luster, is usually clearish to whitish, is soft (H≡2), and rather fragile/brittle. Gypsum has 3 cleavage planes, one of which is well developed (“one good cleavage), and the other two are not well developed (“two poor cleavages”). Broken gypsum specimens are frequently thin plates - the consequence of the one good cleavage plane. Unbroken crystals show monoclinic symmetry. Gypsum has economic value as a mineral. It is the starting ingredient for making plaster and wallboard.------------------------------------From exhibit signage:The silver mines at Naica, Chihuahua, Mexico yield some of the world's finest and largest crystals of gypsum. The crystals form deep underground in cavities or fissures and are unearthed during mining operations. These specimens were preserved and donated by the Fresnillo Mining Company.------------------------------------Locality: deep subsurface cavity at silver mine, Naica, Chihuahua State, northern Mexico------------------------------------Photo gallery of gypsum:www.mindat.org/gallery.php?min=1784 |
| 撮影日 | 2013-10-26 14:25:30 |
| 撮影者 | James St. John |
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