Minerals and Metals in Ancient India v2.c43.s3.t2.1

v2.c43.s3.t2.1

It has been indicated in Table 7.2 that pure corundum (*kuruvinda*) is colourless, and specific lattice substitutions in Al₂O₃ induce specific colour and produce gems such as red ruby or *padmarāga*, blue sapphire or *indranīla*, etc. These three minerals have high hardness (9), and only diamond is harder than them (*AM*, 238). Kauṭilya mentioned the use of *kuruvinda* as an abrasive (AS, 2.14.48).