You searched for: “a diamond
diamonds, a diamond
These are the hardest and most lustrous gems because they retain their brilliance and polish for many generations.

They are a form of carbon that has been crystallized under great pressure and very high temperatures.

The two major sources for diamonds are South Africa and Australia.

"In 1695, two scientists obtained a diamond from a rich patron and heated it by using a lens to focus light on it. The diamond disappeared. Diamond is made of carbon, and it burns just as coal will when it is heated strongly enough."
Isaac Asimov's Book of Facts by Isaac Asimov;
Bell Publishing Company; New York; 1981; page 424.
This entry is located in the following unit: Gemstones or Precious and Semi-Precious Stones + (page 1)
(the four gemstones which are most valuable are diamonds, sapphires, rubies, and emeralds; and anyone would be impressed with a gift of a diamond, a sapphire, an emerald, or a ruby piece of jewelry)