Calcite

==Calcite is a colourless or white mineral. The largerst Calcite was found in Iceland that measured 7x7x2 m and 6x6x3 m and it weighted about 250 tons. Calcite can be found in volcanic or mantle-derived rocks. The steak is white, the fracture is conchoidal, the hardness is 3 and the luster is from pearly to vitreous. Aragonite (another mineral) will change to Calcite when the temperature reaches 470oC.==