Soubor:Calcite crystal (Pugh Quarry, near Custar, Ohio, USA) 4.jpg

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Obrázek ve vyšším rozlišení‎ (rozměr: 2 427 × 2 181 pixelů, velikost souboru: 3,48 MB, MIME typ: image/jpeg)

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• English: Calcite from Ohio, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, 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 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 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.

• Locality: Pugh Quarry, near Custar, northwestern Ohio, USA
• Photo gallery of calcite: www.mindat.org/gallery.php?min=859
• Date: 24 March 2018, 12:22:36
• Source: Flickr.com
• Author: James St. John

FLICKR – https://www.flickr.com/photos/jsjgeology/40184013125/

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	Datum a čas	Náhled	Rozměry	Uživatel	Komentář
současná	24. 1. 2021, 11:47		2 427×2 181 (3,48 MB)	Sysop (diskuse | příspěvky)	(Fotografie + )

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