Diamonds are a Girl's Best Friend - They look beautiful, they are shiny and they last forever - as in the James Bond film - Diamonds are Forever.
Diamonds are made from Carbon - that's essentially the lead from a pencil subjected to intense pressure and temperature - Temperatures from 1650 to 2370 F and pressures between 45 and 60 kilobars. Although diamonds are very resistant to damage, they can be burnt (at temperatures of 1400 F and can be shattered by other diamonds. They have been formed generally about 100 miles under the surface of the earth and then pushed to the surface either by volcanic or other means and are generally very old - 1 to 3.3 Billion years old (That's 22% to 73% of the age of the earth.
There are four characteristics (The 4 "C's") which describe a diamond -
1. Carat - A Unit of weight for Gemstones which is not to be confused with Karat - an amount of gold in an item.
A Carat is defined as 200mg (1/5g) and can be further divided into "Points" where 1 point = 0.01 Carat.
2. Cut (Proportions, Symmetry and polish)
3. Colour (How close to colourless - or how intense the hue of a coloured diamond)
4. Clarity (free from inclusions or defects.
Mined diamonds look similar to a small chunk of glass and need to go through a process called "Cutting" to look right - this is a very delicate procedure involving studying the diamond - often now with x-ray diffraction to choose optimal cutting directions. After an analysis which sometimes can take years in the case of large diamonds, the stone can be cut with a sharp blow with a hammer and pointed tool (a very quick but risky procedure) - alternatively it can be cut with a diamond saw (reliable but very laborious). After initial cutting, the diamond is shaped by polishing which is extremely time consuming.