Minerals and Metals in Ancient India v2.c43.s1.t1.6

v2.c43.s1.t1.6

| Name English / Sanskrit | Colour | Hardness (Moh’s Scale) | Reasons for Non-white Colour |
| Lapis Lazuli/Ultramarine/rājāvartal lajhward (Glass has hardness 5-5-1/2) | Deep azure blue | 5-½ | The constituent minerals are Sodium-Calcium-Aluminium silicates with sulphate and polysulphide (S₃) anions. The 19 outer electrons of S₃ unit undergo transitions within the molecular orbitals. These produce absorption band in the yellow range and hence intense blue colour. Less sulphur in the mineral system gives green colour which makes the gem less worthy. |
| Pearl/muktā | Usually white | 3-4 | Iron, manganese etc. possibly complexed with organic matter, so that the colour is perishable on heat. |
| Coral/pravāla/ vidruma | red, black etc. | 3-4 | Iron, manganese etc. possibly complexed with organic matter, so that the colour is perishable on heat. |