Gemstone usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons. Gemstones are classified into different "groups", "species", and "varieties". For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow) and morganite (pink), which are all varieties of the mineral species beryl. Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture and luster. They may exhibit pleochroism or double refraction. They may have luminescence
Gemstone File Originally distributed in 1975 by hand and mail in photocopy form, the Gemstone File has appeared in slightly revised form in Hustler magazine and on the Internet. Roberts, known only to Stephanie Caruana and conspiracy theorist Mae Brussell, purportedly began gathering information in the file when Howard Hughes stole his invention for processing synthetic rubies, hence the title "Gemstone". According to Gerald Carroll, Roberts was born in New York State on October 27, 1919 and died of lung cancer in San Francisco on July 16, 1976. "Factsheet Five" publisher Mike Gunderloy collected and distributed several versions of the Gemstone File.