Natural DiamondsNatural diamonds are classified by the type and quantity of impurities found within them.
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Type Ia - Thi
s is the most common type of natural diamond, containing up to 0.3% nitrogen.
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Type Ib - Very few natural diamonds are this type (~0.1%), but nearly all synthetic industrial diamonds are. Type Ib diamonds contain up to 500 ppm nitrogen.
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Type IIa - This type is very rare in nature. Type IIa diamonds contain so little nitrogen that it isn't readily detected using infrared or ultraviolet absorption methods.
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Type IIb - This type is also very rare in nature. Type IIb diamonds contain so little nitrogen (even lower than type IIa) that the crystal is a p-type semiconductor.
Synthetic industrial diamondsSynthetic industrial diamonds are produced the process of High Pressure High Temperature Synthesis (HPHT). In HPHT synthesis, graphite and a metallic catalyst are placed in a hydraulic press under high temperatures and pressures. Over the period of a few hours the graphite converts to diamond. The resulting
diamonds are usually a few millimeters in size and too flawed for use as gemstones, but they are extremely useful as edges on cutting tools and drill-bits and for being compressed to generate very high pressures.
Thin Film DiamondsA process called
Chemical Vapor Deposition (CVD) may be used to deposit thin films of polycrystalline diamond. CVD technology makes it possible to put 'zero-wear' coatings on machine parts, use diamond coatings to draw the heat away from electronic components, fashion windows that are transparent over a broad wavelength range, and take advantage of other properties of diamonds.