This site from the Wikipedia encyclopedia gives a definition and information on hardness, value determination, and natural versus artificial rubies. Links are provided throughout for additional information on related subjects.

This site will identify your birthstone based on a particular birth date and provide information on that gem. More information can be learned about that gem, and others, in their Gem Library.

This thorough site covers the history of jade along with how jade is sold and used today.

Properties, myths, and facts of zircon are depicted in this commercial site.

Site provides many fun facts about the gem peridot, including information on its history and physical and metaphysical properties. Also provides a picture of the gem itself.

This commercial page gives information about the physical properties of zircon, its appearance, and where it can be found. Includes pictures and tables.

Article on the mineral beryl with a section on aquamarine, which is a variety of beryl.