Diamond is one of Earth’s great rarities, and great steps are taken to mine it. Approximately 130 million carats of diamond are mined each year, and about 80% of these are not suitable for being cut and set into jewelry, either because they are too small, or discolored, or otherwise of non-gem quality. So, what do the miners do with these diamonds they labored so hard to gain? Remember, diamond is the hardest natural substance known to man. What better way to use these diamonds than for drill bits and grinding wheels?
The diamonds, embedded in the steel, will not wear down for years even if used in regular use, and are the best abrasives on the market. I myself have quite a lot of bits that I use very regularly for grinding stones, and let me tell you, they are awesome! Unfortunately, if being used to grind steel, the steel tends to retain the heat created by the friction, and so causes the diamonds to come loose from their imbedment in the bit’s surface. I’ve lost a few good bits that way.
Because of diamond’s cubic crystal growth, there are always sharp points and edges, which catch onto the surface of the stone being ground, resulting in a very fast grind. Often, extremely fine grains would be used in polishing wheels, which result in the surface being polished to a mirror finish. The larger the grains, the faster, but rougher, the grind.