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 to uneven
Specific Gravity2.71
Colorsbrown, white, yellow, colorless, pink, green, blue
Transparencytranslucent
Type LocalityCardiff
Mineral GroupCarbonates
Usescement production, construction material, soil conditioner, optical instruments, collector specimens
Associated Mineralsquartz, pyrite, galena, sphalerite, fluorite
Raritycommon
Description
This specimen is a rough, blocky piece of brown calcite, exhibiting a crystalline texture with varying shades of light to dark brown and some lighter, almost white areas. Its surfaces show characteristic cleavage planes.
Geological Context
Calcite is a very common mineral found in sedimentary rocks (limestone, chalk), metamorphic rocks (marble), hydrothermal veins, and as a primary mineral in igneous rocks. It forms in a wide range of geological environments.
