Cochise College Student Papers in Geology
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Roger Weller, geology instructor
Amethyst
Justine Andrews
Physical Geology
Fall 2006
Amethyst
Amethyst derived its name from Middle English amatist and from Latin
Amethystus meaning not drunk or intoxicating. The Amethyst is an affordable
purple gemstone that is used in jewelry and is often used to show royalty and
nobility. The association of royalty makes it popular with the leaders of
modern society and it gives them the feeling of being “kings” in their areas.
The Amethyst gemstone is also used for the month of February and is often given
at the 4th and 6th wedding anniversary. The Amethyst is
the most valuable transparent, coarse- grained variety of the silica mineral
quartz that is valued as a semi-precious gem for its violet color.
photo by R.Weller
Mines
Amethyst is mined in Brazil, Uruguay, Sri Lanka, Siberia, Canada, India, Bolivia, and Argentina and in the U.S.; most of the Amethyst comes from Zambia. The Amethyst can be found in many places and are not the same they are all very different and unique to that area where they are found. Their color, shape, inclusions and associations of formations can help identify them. Experts use these characteristics to identify the gemstone and the mine it came from.
Brazil: The mines in Brazil are considered to be the best in the world. These mines are located in del Sul, which is near Uruguay. They have hundreds of working mines all of which are mined by hand. The workers use small-motorized carts to help them remove the large and excess rocks. The cavities are filled with water and dissolved minerals permeated through the rock. With time these minerals will crystallize in the cavities, and line the cavity of the rock with a silica layer (amethyst). The geodes are continually developing as long as there is moisture present. When the geodes are ready they will blast away the rock and then look for any undamaged geodes. Once they find them they will then drill a small hole to determine the quality and the shape of the cavity. It may take these miners a long time to do the procedure. They must be very carefully chipped away out of the geode with very little damage. The crystals that are produced in this area vary in color from pale to medium purple color.
entrance to the mine in
Brazil geodes that are in the cave wall
These are some of the Amethysts that are from
Brazil
http://www.crystal-world.com/html/mining/international/brazil.htm
Amethyst in the U.S.:
There are many places in the
U.S. where you can locate the amethyst crystal. Some of the places are Maine,
Pennsylvania, and North Carolina to Montana, Colorado and Arizona. The color of
the American Amethyst ranges from medium to dark purple and some include a smoky
crystal. In North Carolina the crystal has a bluish tint in some, which makes
it unique to that state. Colorado has clusters that are formed in cavities
within sandstone.
Credit photo to Four Peaks Arizona
Amethyst mined at Four Peaks Arizona, is found between the third and fourth peak from the left. This peak is privately owned and located at the end of a steep and rocky trail. In the 1500’s, the Spanish explorers were said to have gathered the amethyst and were used in making crown jewels. Amethysts come from the cavities within an old fault zone, and are mined by hand and sent to the city to be cut. Amethysts that are mined here are classified as “Siberian” quality; meaning they are a higher grade of amethyst, and they display a reddish-violet hue color. These mines were closed for some time and were reopened about 5 or 6 years ago and some of the gems were shown at the Tucson gem show in 1999.
http://www.mtlilygems.com/mineinfo/4pksspc.html
These are amethyst druses and individual crystals from Four Peaks, Arizona.
picture credited to Four Peaks Arizona
This is a picture of what an Amethyst looks like before it is cut and facetted. In this picture you are able to see the reddish purple gem with hematite crystal points.
Uruguay Amethyst:
The amethyst that you
find here are mined in large “vugs”, or volcanic pockets. These vugs have a
brown or gray exterior that contains stalactites. On top of these the formation
of the Amethyst druses takes place. These crystals are less uniformly colored
and the crystals often bond with multicolored agate and this will sometimes
leave a yellow or red tinge to the stone.
credit photo to Stones Precious
Mines in South America Between Argentina and Brazil
credit photo to Stones Precious
Up close of the amethyst inside the geode
http://www.stonesemiprecious.com/images/products/citrine_druzes/
Citrine is an orange-yellow color that is rare and is created by heating amethyst. There are others like the milky quartz, rock crystal, rose quartz, and the smoky quartz. The finest quality of the Amethyst is medium to dark in tone, vivid in intensity and in the color purple, ranging from reddish purple to bluish purple in hue. The deeper the color purple the more valuable it is.
photo by R.Weller
Amethyst is often cut as brilliant round cuts to
maximize the color, because of the patchy ness of the color distributes in the
crystals. Some other cuts may be used when the color is better distributed.
The cut gems are graded using the terms: Siberian, Uruguayan or Bahain; this
represents the high medium and low grade respectively.
I chose the Amethyst for a couple of reasons, one it is my birthstone and two because I think it is a pretty gemstone. I had a lot of fun doing this paper and finding out a lot about it. The mining was the most interesting to me and may be one day I will be able to see one my self.
www.stonesemiprecious.com/index.shtml
http://mineral.galleries.com/minerals/gemstone/amethyst/amethyst.htm
http://bedrockfossils.com/amethyst.html
http://www.jewelinfo4u.com/Amethyst_mines.aspx
http://www.crystal-world.com/html/mining/international/brazil.htm
http://skywalker.cochise.edu/wellerr/aawellerweb.htm