State six physical properties of a diamond:
1. It is the hardest naturally occurring solid. Amongst the diamonds, the black diamonds are the hardest.
2. A pure diamond is a (i) colourless, (ii) transparent, and (iii) brittle solid.
3. A pure diamond is transparent to X-ray and the visible light.
4. The density of pure diamond is 3.5 gcm³,
5. It is a very poor conductor of heat and electricity.
6. It is insoluble in all solvents.