JASPER
never worn by lovers, nor was it worn at night, as it provoked nightmares. Prase, which means leek in Greek, is a pale green form of jasper. Prase is often included in the opal family, as one of the common opals. (Common opals lack the flash and fire precious opals are noted for. See: http://www.suite101.com/article.cfm/gems...) There's also a green stone recently discovered in Australia that has been named Imperial prase by its discoverers. They chose that name because it resembles chrysoprase. Their choice of name may or may not be recognized by mineralogists.
Sard is a reddish-orangish brown stone that was often paired with onyx by the ancients in the belief that the positive effects of red would dispel the negative aspects of the black onyx.
Sardonyx is very similar to onyx in that it has parallel stripes, and similar to sard in that the stripes are alternating reddish-brown and white. People wore sardonyx next to their hearts to heal depression. It was also thought to improve communication.
Tiger's eye starts life as crocidolite, an asbestos-like mineral. Over time, quartz replaces the crocidolite fibers, creating a silky-looking yellowish-brown gemstone. Tiger's eyes get their name from their chatoyancy. Chatoyancy refers to the appearance of an eye moving across the stone as it is rotated. (See Special Reflections: http://www.suite101.com/article.cfm/gems... ). The jasper family also includes petrified dinosaur bone and petrified wood. In both these instances, the original organic material was replaced by quartz. (This process is also called fossilization.) The replacement substance retains the same shape of the animal or plant. By its very nature, petrified material is ancient.
Turritella is very similar to petrified dinosaur bones, in that it's snail shells in which the original organic material has been replaced by quartz. It's found primarily in the state of Wyoming.
All the jaspers are cut into cabochons (rounded shapes) rather than faceted. Most are also made into beads or carved into ornamental objects. Like the other members of the quartz family, jaspers are found worldwide.
Sites:
http://www.gemhut.com/jasper.htm
Basic information about jasper, and a photo
Click on each variety in the list partway down the page
for more photos
http://www.minerals.net/mineral/silicate...
Information about jasper, including a list of all the
varieties
http://www.gemstone.org/onyx.html
Picture of onyx jewelry, and general information,
including the story of how it was named
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