Minerals and Metals in Ancient India v2.c47.24

v2.c47.24

**Calcite** : CaCO₃. Hardness 3. Highly birefringent. In crystal form also known as Calc Spar, Iceland Spar, Satin Spar etc. In granular massive to crypto-crystalline kind occurs as rock limestone, marble (meta-morphic, higher density) and chalk. Various colours due to impurities. Onyx marble (banded) also known as *oriental alabaster*. Chalk, composed of the shells of minute sea organisms, leaves a trace on a board.