CALCITE

 

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.

 

Calcite cleavage rhombs (both are 3.2 cm across)

Left: optically clear calcite ("Iceland spar").

Right: optically clear, pale pinkish calcite.

 


 

Calcite - unbroken hexagonal crystal from the Cumberland Mine, Smith County, Tennessee, USA.

 


 

Calcite from Dalnegorsk, Maritime Province, eastern Russia.  Specimen owned by Terry Huizing.

 


 

Calcite - unbroken crystals from Hubei Province, east-central China.  Specimen owned by Terry Huizing.

 


 

Calcite from Guangdong Province, South China.  Specimen owned by Terry Huizing.

 


 

Calcite from cavities in Deccan Traps flood basalt (Cretaceous-Tertiary boundary, 65 m.y.), Jalgaon District, northern Maharashtra State, west-central India.  Specimens owned by Terry Huizing.

 


 

Calcite - helictite from the Santa Eulalia Mining District in Chihuahua State, Mexico.

 


 

Calcite on fluorite from the Rosiclare Level, Cross-Cut Ore Body, Minerva # 1 Mine, Cave-in-Rock Mining District, southern Illinois, USA.  Specimen owned by Ross Lillie.

 


 

Calcite from Yunnan Province, southwestern China.  Specimen owned by Terry Huizing.

 


 

Calcite "straws" from the Second Sovietskiy Mine, Dalnegorsk, Maritime Province, eastern Russia (Dwyer Mercer County District Library # 200-125, Celina, Ohio, USA).

 


 

Poker-chip calcite from Charcas, Mexico (Dwyer Mercer County District Library # 222-450, Celina, Ohio, USA)

 


 

Calcite sand rose from Fontaineblue, north-central France (CSM # 53397, Colorado School of Mines Geology Museum, Golden, Colorado, USA).

 


 

Calcite from Aurangabad, India.  Specimen owned by Terry Huizing.

 


 

Cobaltoan calcite (a.k.a. cobaltocalcite) (3.8 cm across) from Shaba/Katanga Province, Zaire ("D.R. Congo").  Cobaltoan calcite is a deep pinkish-purple variety of calcite having significant cobalt impurity - (Ca,Co)CO3.

 


 

Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit in the Second Sovietskiy Mine at Dalnegorsk, Maritime Province, eastern Russia.  Manganoan calcite is a pinkish calcite with significant manganese impurity - (Ca,Mn)CO3.

 


 

Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit at Dalnegorsk, Maritime Province, eastern Russia.  Specimen owned by Terry Huizing.

 


 

Manganoan calcite (a.k.a. manganocalcite) from a skarn deposit at the Huanzala Mine, Huallanca District, Dos de Mayo Province, Huánuco Department, Peru.  The skarn deposit is developed along a felsic dike that has intruded limestones of the Lower Cretaceous Santa Formation.  Specimen owned by Terry Huizing.

 


 

Photo gallery of calcite

Photo gallery of cobaltoan calcite

Photo gallery of manganoan calcite

 


 

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