Natural abrasive

Natural abrasive

(a) Non- Siliceous Abrasives
It is a pure crystalline carbon. It is the hardest known substance. Its hardness is 10 on Moh’s scale. It is chemically inert and not affected by acids or alkalis. The off- colour diamond is called borts and black colour diamond is called carbonado.

Uses : It is used in drill points, cutting rocks, stones and grinding wheels.

2. Corundum
It is a pure crystalline alumina (Al2O3). Its hardness on Moh’s scale is 9.

3. Emery
It is a used for grinding glasses, gems, lenses, metals,etc.

(i) 55-75% crystalline alumina,
(ii) 20-40% magnesite,
(iii) 12% other minerals.

Uses : It is a used in the tip of cutting and drilling tools, and also it is used in making abrasive paper and cloth.

(b) Siliceous abrasive

1. Quartz
It is pure crystalline silica (SiO2). Its hardness is 7 on Moh’s scale.

Uses: It is used for grinding pigments in the paint industry and also as granules in grinding machines.

2. Garnet
It is a mixture of trisilicates of alumina magnesia and ferrous oxide. Its hardness ranges from 6-7.5 on Moh’s scale.

Uses : It is used in making abrasive paper and abrasive cloth and also in glass grinding and polishing metals.