Calcareous Spar
A carbonate of lime, occurring principally in grayish-white crystals. It is infusible, falls into quicklime before the blowpipe, and effervesces with acids; its composition is lime 57, carbonic acid 43. This mineral is of universal occurrence, and sometimes it is found tinged with various shades of color, owing to the presence of manganese, iron, and other impurities.