Why is coal black and diamonds white? Both are made of carbon

Both diamond and coal are made up of carbon but the crystalline structure of these two isotopes of carbon varies giving more prestige to diamond rather than coal. Hence diamonds are transparent and coal is black.

While coal has a normal hexagonal crystalline structure in which carbon atoms are arranged in the shape of a hexagon, diamond atoms are compressed under heat and pressure to give an octagonal shape to it. Moreover, the carbon atoms in coal are arranged along a plane while in diamond the atoms arrange themselves in pyramidal form.

This heat compression may happen due to earth’s movement and subsequent pressure for millions of years. Nowadays, artificial diamonds can be prepared by external application of heat and pressure.

Both diamond and coal are found in mines. They remain mingled with each other and one needs to extract and separate the two substances. Afterwards, diamond is cut so that light entering into it suffers from total internal reflection and hence the brightness of the precious stone!

While the flat planes of coal can absorb all wavelengths of light, the diamond atom’s pyramidal plane reflects and refracts rays of unequal wave length. Thus diamond sparkles when light falls on it.