The diamond stone

   Diamond, pure carbon, Symbol C. Brilliant, nonmetallic luster. Colorless or various colors. Transparent to opaque. Hardness 10. Specific gravity 3.52.

   Diamond is one of three pure forms of carbon, the other two being graphite and carbon black. While graphite and carbon black are very soft, the unique arrangement of the carbon atoms in the diamond makes it extremely hard and dense.
   The great beauty and scarcity of transparent diamonds make them highly valued as gems. The diamond is the birthstone for the month of April, and it is by far the most popular gem for engagement and wedding rings. The diamond is also an ideal industrial tool because it is the hardest natural substance known.
   The unit of weight for gems and industrial diamonds is the metric carat. One metric carat is equal to 0.2 grams or to 0.007 ounces.
   Men have long been fascinated by unusually large and beautiful diamonds. One of the earliest known large stones was the Great Mogul, a famous Indian diamond of about 280 carats. It has been lost since 1665 and may have been cut into smaller diamonds.