Fluorite (Late Cretaceous or Tertiary; Melchor Muzquiz, Coahuila, Mexico) 6 : 無料・フリー素材/写真
Fluorite (Late Cretaceous or Tertiary; Melchor Muzquiz, Coahuila, Mexico) 6 / 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 | Fluorite from Mexico. (centimeter scale)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 about 5400 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 halides are the "salt minerals", and have one or more of the following anions: Cl-, F-, I-, Br-.Fluorite is a calcium fluoride mineral (CaF2). The most diagnostic physical property of fluorite is its hardness (H≡4). Fluorite typically forms cubic crystals and, when broken, displays four cleavage planes (also quite diagnostic). When broken under controlled conditions, the broken pieces of fluorite form double pyramids. Fluorite is a good example of a mineral that can be any color. Common fluorite colors include clear, purple, blue, green, yellow, orange, and brown. The stereotypical color for fluorite is purple. Purple is the color fluorite "should be". A mineral collector doesn't have fluorite unless it's a purple fluorite (!). Fluorite occurs in association with some active volcanoes. HF emitted from volcanoes can react with Ca-bearing rocks to form fluorite crystals. Many hydrothermal veins contain fluorite. Much fluorite also occurs in the southern Illinois area (Mississippi Valley-type deposits).The fluorite shown here is from a Mississippi Valley-type deposit in northeastern Mexico. Fluorite mineralization occurs in the upper Georgetown Limestone (Lower Cretaceous) and formed by reactions with migrating, fluorine-rich, basinal fluids generated during the Laramide Orogeny. The latter is a mountain building event that occurred in western North America during the Late Cretaceous and early Tertiary. The event formed the true Rocky Mountains.Locality: unrecorded mine in Melchor Muzquiz Municipality, Coahuila State, northeastern Mexico------------------------See site-specific info. at:www.mindat.org/loc-31356.html------------------------Photo gallery of fluorite:www.mindat.org/gallery.php?min=1576 |
| 撮影日 | 2017-04-19 16:59:41 |
| 撮影者 | James St. John |
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