Calcite

Real mineral · common · CaCO₃

The most stable polymorph of calcium carbonate and the primary component of limestone and marble. Exhibits perfect rhombohedral cleavage and strong birefringence. Dissolves slowly in acidic water, forming cave systems over geological time.

Identity

Formula

CaCO₃

Chemical class

carbonate

Mineral group

Rhodochrosite, Siderite, Smithsonite

Also known as

Iceland spar (optical variety), Chalk (earthy variety)

Crystallography

Crystal system

trigonal

Habits

rhombohedral, scalenohedral, prismatic, massive, stalactitic

Fracture

conchoidal

Physical properties

Mohs hardness

3

Density

2.71 g/cm³

Luster

vitreous, pearly

Colors

colorless, white, yellow, pink, red, blue, green, black

Streak

white

Transparency

transparent, translucent, opaque

Geology

Origins

sedimentary, hydrothermal, metamorphic

Host rocks

limestone, marble, chalk

Associated minerals

Quartz, Fluorite, Dolomite, Pyrite

Geography

worldwide

Classification

Rarity

common

Gem quality

No

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