Gem stones were formerly classed as precious, semiprecious, and ornamental stones. Today this classification is largely replaced by the broader term gem materials. The following list includes the major gem materials and some of the less important ones. A colorless variety of tourmaline. The markings of moss agates occasionally resemble natural objects and so were much prized in the past.
Most agates are naturally grayish and are artificially colored.
They are usually soaked in solutions of sugar or honey and acid or salt solutions and then heated. Named after Alexander II of Russia. A variety of chrysoberyl, grass green in color. Shows a red hue in artificial light. Amazonite, or Amazonstone.