Carbonate minerals and their features
Carbonate minerals are those minerals containing the carbonate ion, CO2−3.
Aragonite
Chemical Formula : CaCO3
Crystal System : Orthorhombic
Mohs Scale : 3.5 - 4
Specific Gravity : 2.94
Tenacity : Very brittle
Weight : 14.41 g
Common impurities : Pb , Sr (strontium) , Zr
Smithsonite
Chemical Formula : ZnCO3
Crystal System : Trigonal
Mohs Scale : 4.5
Common impurities : Co,Cu,Mn,Ca,Cd,Mg,In
Calcite
Chemical Formula : CaCO3
Crystal System : Trigonal
Mohs Scale : 3
Malachite/Azurite
Chemical Formula of Malachite : Cu2CO3(OH)2
Chemical Formula of Azurite : Cu3(CO3)2(OH)
Crystal System : Monoclinic
Mohs Scale : 3.5 - 4
Specific Gravity : 3.6 - 4
Tenacity : Brittle
Azurite is unstable in open air compared to malachite, and often is replaced by malachite.This weathering process involves the replacement of some of the carbon dioxide (CO2) units with water (H2O), changing the carbonate:hydroxide ratio of azurite from 1:1 to the 1:2 ratio of malachite:
2 Cu3(CO3)2(OH)2 (Azurite) + H2O → 3 Cu2(CO3)(OH)2 (Malachite) + CO2
Popcorn Calcite
Calcite
From Manisa, Turkey
Calcite
Chemical Formula : CaCO3
Crystal System : Trigonal
Mohs Scale : 3
Specific Gravity : 2.71
Tenacity : Brittle
Weight : 48.86 g
Common impurities : Fe, Mg, Zn and Co
Calcite
From Manisa / Turkey.