Calcite
Image: <a href="//commons.wikimedia.org/wiki/User:Strekeisen" title="User:Strekeisen">Strekeisen</a> (CC BY-SA 4.0)
Mineral NameCalcite
Chemical FormulaCaCO3
Mohs Hardness3
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
CleavagePerfect rhombohedral in three directions
Fractureconchoidal to uneven
Specific Gravity2.71
Colorswhite, colorless, grey, yellow, green, pink, blue, brown
Transparencytransparent to translucent
Type LocalityNot specified in metadata
Mineral GroupCarbonates
Usesconstruction, agriculture, optical instruments, chemical industry, collector
Associated Mineralsbasalt (host rock), plagioclase, pyroxene, olivine
Raritycommon
Description
This microscopic image, taken under crossed nicols, shows bright, iridescent calcite crystals filling rounded vesicles and thin fractures within a dark, fine-grained basaltic matrix.
Geological Context
Calcite frequently forms as a secondary mineral, precipitating from hydrothermal fluids or groundwater to fill vesicles (gas bubbles) and fractures in volcanic rocks such as basalt, a process known as amygdaloidal infilling.
