When people talk of a diamond, they think about a piece of sparkling jewelry costing millions of dollars. But for those obsessed with chemistry, a diamond is no more than carbon in its concentrated form. Because diamond is just that, a concentration that is mainly carbon that sometimes contains traces of boron and nitrogen. But there are mineral graphites that are similar in composition to diamonds, yet they are not as well-known and as well-loved as diamonds. The answer has something to do with the crystal structure or the arrangement of the carbon atoms in diamonds. A crystal structure is used to distinguish the properties of a mineral.
The carbon in a diamond shares all of its four electrons with carbon atoms that are near them. Together, they form a tetrahedral unit. The electron pair bonding makes up the covalent bond. The structural unit of the diamond is made up of 8 atoms that form a cube.
A diamond is typically colorless. The variations of color that people see are actually results of adding various chemicals. For example, by adding boron, the diamond turns blue and adding nitrogen makes a diamond yellow. A pure diamond is colorless because there is insufficient energy from visible lights to affect its electrons, so that no lights are absorbed. It is only when chemical impurities like boron, nitrogen, and hydrogen are present that the electron states are affected by energy in visible light.
On Mohs hardness scale, diamond scores 10 because it is the hardest known natural material. In comparison to copper, diamond is about four times better when it comes to thermal conduction. Although, diamonds do not transmit electricity that well, some diamonds are used as semiconductors. When treated to a high temperature, a diamond will burn. It has a high specific gravity and very dense due to the low atomic weight of carbon. Its ability to expand is low and chemically inactive with respect to acids and alkalis. Because diamonds have negative electron affinity, they will withstand and repel water, but will admit hydrocarbons such as grease or wax.
Basically, there are three types of diamonds: natural, synthetic industrial diamonds, and thin film diamonds. Natural diamonds are identified by the type and amount of impurities found within them. For example, Type Ia, the most common natural type of diamond contains up to 0.3% nitrogen, while Type Ib contains as much as 500 ppm nitrogen. However, only -0.1% of diamonds are of this type. Synthetic industrial diamonds are diamonds that are created through the process known as High Pressure High Temperature Synthesis. Because the resulting diamonds contain too many flaws, they are not used as gemstones rather they are used as edges on drill bits and cutting tools. They are also compressed to produce high pressures. But diamonds are never used as machine alloys because they wear off quickly. Deposits of thin films of polycrystalline diamonds are made using the process known as Chemical Vapor Deposition. The diamonds here are used as coatings on machine parts.