Calcite
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/14730981@N08">James Petts</a> from London, England (CC BY-SA 2.0)
Mineral NameCalcite
Chemical FormulaCaCO3
Mohs Hardness3
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavageperfect rhombohedral in three directions
Fractureconchoidal
Specific Gravity2.71
Colorsbrown, tan, white
Transparencytranslucent
Type LocalityCardiff
Mineral GroupCarbonates
Usesconstruction, agriculture, optical, chemical, collector
Associated Mineralsquartz, feldspar, pyrite, galena, sphalerite
Raritycommon
Description
A blocky, rough specimen of brown calcite, exhibiting varying shades of brown with some lighter, translucent areas. The surface shows some crystalline texture and natural fractures.
Geological Context
Calcite is a common rock-forming mineral found in sedimentary rocks (limestone, chalk), metamorphic rocks (marble), and as a vein mineral in hydrothermal deposits. It forms from the precipitation of calcium carbonate.
