Onyx stone

   Onyx is a semi-precious stone. Greek myths spoke of onyx as the fingernails of a goddess which were turned into stone as they touched water. The name onyx comes from the Latin word, oniscus, which means "lined" or "partly transparent," as a fingernail. The lines in this stone are parallel. They are white with brown, red, or green variations.
   True onyx is a variety of agate, which is a form of quartz. It is formed from the dissolved mineral silica, which has been deposited in areas of ancient lava beds or petrified wood. The colors are caused by the deposition of other minerals. Mexican onyx is actually miscalled because it is a limestone variety, frequently found as cave or hot springs deposits. This is sometimes called onyx marble. It is more translucent than the true onyx.
   Onyx is easily carved and takes a high polish. It is used as jewelry, ornamental stonework, mantles, and pillars.