Tuesday, September 17, 2013

Gemstone of the Week: Andalusite

(Image of Andalusite found on gemselect.com)

Andalusite is trimorpheous with of Sillimanite and Kyanite.  This means that the chemical composition of the three gems is the same, but with a different crystal structure. It was discovered in 1789, but not given a name until 1798 when it was named by Jean-Claude Delamétheri.  It was named after the "Andalusia Region" in Spain where it was believed to have been duscovered. However, this assumption that Andalusite was from Andalusia was actually incorrect, the location where it was first discovered (El Cardoso (Guadalajara)) is not in the Andalusia Region.  Not only that, but the Chiastolite variety of Andalusite was already known and been described in a 1754 publication. The Chiastolite variety of Andalusite is opaque gray or brown stone with black inclusions which are symmetrically arranged and generally form an X-shaped cross when cut in a cross section.  The transparent to translucent variety of Andalusite may be pink, red-brown, violet, yellow, green, white, or gray.  It has a hardness of 6.5-7.5 making it great for most any form of jewelry.  It's luster may be vitreous, greasy, or sub-vitreous.  Andalusite is a fairly rare gemstone.  Its per carat value ranges depending on the size, colour, and quality of the stones but there is a value chart for Andalusite on GemVal.  Andalusite may be found in: Andorra, Antarctica, Argentina, Armenia, Australia, Austria, Azerbaijan, Belgium, Bolivia, Botswana, Brazil, Bulgaria, Burma (Myanmar), Burundi, Canada (provinces of: British Colombia, New Brunswick, Manitoba, Newfoundland, Labrador. Ontario, Quebec, Northwest Territories, Nova Scotia, Saskatchewan, and the Yukon Territory), Chile, China, Czech Republic, Egypt, Finland, France, Georgia, Germany, Hungary, India, Indonesia, Iran, Ireland, Italy, Japan, Kazakhstan, Madagascar, Malawi, Morocco, Mozambique, Mongolia, Namibia, Norway, New Zealand, Papua New Guinea, Poland, Peru, Portugal, Republic of Macedonia, Russia, Slovakia, South Africa, South Korea, Spain, Sri Lanka, Surinam, Swaziland, Sweden, Switzerland, Tajikistan, Tanzania, Thailand, Turkey, England, Scotland, Ukraine, United Arab Emirates, Vietnam, Zimbabwe, and the states of Wyoming,Wisconsin, Washington, Virginia, Vermont, Utah, Texas, South Dakota, South Carolina, Pennsylvania, North Carolina, New Mexico, New Jersey, New Hampshire, Nevada, Montana, Michigan, Massachusetts, Maine, Indiana, Idaho, Georgia, Florida, Connecticut, Colorado, California, Arizona, Alaska, and Alabama.

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