CHALCEDONY, JASPER, and AGATE
Chalcedony (kal SED' nee) is any form of microcrystalline quartz , where the crystals are too small to be seen without high magnification. However, in the rock world, only the translucent or transparent, single color types are sold as "chalcedony". (The exception would be Carnelian, a blood red variety.) Other colors are white, blue, purple, pink, yellow, orange or red. The various types differ in color due to metallic impurities, such as iron, nickel, copper, and titanium present during crystallization.
Chalcedony forms in rounded crusts, rinds or stalactites in volcanic and sedimentary rocks. The name probably comes from Chalcedon or Calchedon, an ancient port city on the Sea of Marmara in modern-day Turkey. They usually have a waxy luster and a hardness of 7. Chalcedonies are tough gems, good for all jewelry applications and require no special care in wearing or cleaning.
Some varieties of Chalcedony and their localities are:
Chrysoprase – gets its green color from nickel. Most chrysoprase sold today comes from Australia.
Chrysocolla - Marketed as "Gem Silica" this relatively rare, blue to blue-green, opaque to near transparent material is the most expensive type of chalcedony. Found almost exclusively in Arizona its color is due to copper.
Blue Chalcedony -The various blues are generally named by their localities. The colors vary greatly from gray to lavender. They also vary in the amount of translucency.
Bustamite - An extremely rare pink variety from South Africa. It is found in the manganese mines and the color can vary from pale pink, to dusty rose, to a raspberry red.
Carnelian - reddish blood-brown or orange-brown.
JASPER AND AGATES
The rest of the stones in the chalcedony family are sold under individual variety names, or as jasper or agate. While the definitions overlap, Jasper usually refers to an opaque stone, with a solid color or an irregular display of colors caused by various mineral impurities. The named is derived from the Greek word that means “spotted stone”. Agate is defined by its translucency (ability to see light through it), and by its clearly defined pattern or banding of multiple colors. The name is derived from the Sicilian river Achates.
Jaspers and Agates are found all over the world, with certain colors or patterns unique to particular localities. All types take an excellent polish, are trouble free to care for, and hardy enough for all jewelry uses. Most names of jaspers and agates come from their colors or their appearance, or from where they are found.
Some Jaspers named after their localities:
Biggs Jasper(Oregon), Bruneau Jasper(Idaho), Owyhee Jasper(Oregon/Idaho), Morrisonite (Oregon), Deschutes (Oregon), Mookaite (Australia), Botswana Agate (Africa), Coyamito Agate, and Luna Agate (both Mexico), Willow Creek Jasper (Idaho), Succor Creek Jasper (Oregon/Idaho) , Laguna Agate (Mexico), Graveyard Plume Agate (Idaho),