Derived from the from the Greek word “adamas,” meaning “unconquerable,” the diamond is the hardest natural mineral on earth. Although rare, it is a derivative of carbon, which is one the most common building blocks in nature.
 
The diamond crystal is made up of repeating units of carbon atoms, each joined closely to four other carbon atoms via the strongest-possible chemical linkage, covalent bonds. The structural unit of diamond consists of eight atoms, arranged in a cube. This extremely stable and rigid network explains why diamonds are so hard and have such a high melting point.
 
Diamond scores an unequaled 10 on Moh’s hardness scale, and is exponentially harder than the next gemstone on the scale − corundum (sapphire), which scores a 9. Diamond is also an exceptional thermal conductor − four times better than copper, and it is chemically inert to most acids and alkalis, which explains its stability. It is one of only a few materials with electron affinity, which means that it repels water, but readily bonds to hydrocarbons such as wax or grease. A diamond has a high specific gravity, and because of the low atomic weight of carbon is very dense.
 
The typical brilliance and fire that is visible in the polished diamond of a diamond are due to the material’s high dispersion and high refractive index. Diamond has the highest reflectance and index of refraction of any of the known transparent substances.