Question

two chemical properties of diamond

Answer 1

It is also chemically resistant and has the highest thermal conductivity of any natural material. These properties make it suitable for use as a cutting tool and for other uses where durability is required. Diamond also has special optical properties such as a high index of refraction, high dispersion, and high luster.

Diagnostic Properties: Hardness, heat conductivity, crystal form, 

Answer 2

The physical and chemical properties are as follows

Diamond:
Colourless
transparent substance with extra ordinary brilliance due to its high refractive index.
It's quite heavy.
It's extremely hard. (Hardest substance known)
It's doesn't conduct electricity. (Due to absence of free ions)
It has high thermal conductivity and high melting point.
It burns on strong getting to form carbon dioxide.

2. Graphite:

It's a greyish black, opaque substance.
It's lighter than diamond, feels soft and slippery to touch.
It's good conductor of electricity (due to presence of free ions) but bad conductor of heat.
On strong heating, it burns to give carbon dioxide.