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Roger Weller, geology instructor

wellerr@cochise.edu

Amethyst
by Casandra Farmer
Physical Geology
Fall 2014
  
 
 

Amethyst-The Royal Gemstone
 

Amethyst is a purple colored quartz first discovered in 3000 BC. The gemstone was first discovered in Europe where many different superstitious beliefs formed. The ancient Greeks believed it to be able to ward off intoxication, which transferred the Greek word “amethystos”, which means “not drunken”, to amethyst. The Greeks belief was similarly shared with the ancient Egyptians who believed it capable of keeping people from being poisoned. In medieval times, the gemstone was placed under pillows to cure insomnia, allowing the person to sleep and even bringing good dreams. Churchmen from the same time had Amethyst crafted into rings and jewels to bring the wearers divine revelations and wisdom. Over time, it gained the ability to enhance courage, creativity, intuition, psychic development, and self esteem. It also became a gemstone that could deflect anger and protect the wearer against evil. While Amethyst started out as charms for many different things, it was also used to symbolize royalty. Now, most people know amethyst as the birthstone for February. As such, many people see it as an affordable accessory that can add the look of royalty when bought in the right shade of purple.

     Most sellers of amethyst will heat treat the stone to change the color, turning dark purple into lighter shades. To do this, the heat treatment must be at least 248.9 degrees Celsius. However, some heat treat amethyst to change the color all together. Citrine is another type of quartz, only this one is yellow in color. If dark purple is heat treated to get a lighter shade then the lighter shades are heat treated to get yellow. Citrine is achieved through temperatures between 400 and 500 degrees Celsius. These temperatures will also create a gemstone known as ametrine which is a mixture between amethyst and citrine. There are also times when the amethyst turns green. Traders have given “green amethyst” the name “prasiolite”, but it is still more commonly known as “green amethyst”. Since amethyst is found in geodes, most of them are shaped in stubby pyramidal crystals, but there are several locations where the purple gemstone ends up forming into tall prismatic crystals.
 

Picture taken by April Tucker
 

Picture taken by April Tucker
 

Picture taken by April Tucker
 

While amethyst might have first been discovered in the European area, the largest deposits of the gemstone can be found in Southern Brazil and Uruguay, and Madagascar also has a well known deposit of it. Amethyst’s chemical name is Silicon Dioxide or SiO2 meaning that the gemstone is made up of sulfur and oxygen. Amethyst geodes mainly form in igneous and metamorphic rocks but are also capable of forming within ancient cracks or faults and volcanic gas bubbles. It was also originally believed that the purple color was a result of the addition to manganese. Today, some people instead believe that the color is caused by Ferric Thiocynate. The richness of the color is determined by the amount of iron in the gemstones. Since amethyst is a quartz, it was originally just a quartz. It was changed into amethyst through shifts in the earth’s crust. This will sometimes cause markings to appear on the crystal that look similar to ripples. These markings are known as “thumb markings” and are due to fractures inside of the crystal. As a quartz, Amethyst is rated at the 7th spot on Moh’s scale, making it around the 3rd hardest stone found on earth with only 1/15 of a diamond’s hardness.
 

Amethyst is known as the most valuable of the quartz crystals. Since Quartz is the most common mineral on Earth, amethyst was easily available and affordable. However, with most resources on the planet, it is unsure if the deposits of amethyst will hold up to demand. The gemstone is most popular as jewelry, but there are plenty of people who prefer the gemstone as decorations, keeping them in their original form and merely cleaning out the geode and polishing the rough edges of the opening. The gemstone forms differently in each of these places so each places deposit is better suited towards one use than the other. Africa and Australia are more known for small amethysts, but they are also rich in color. On the other hand, Brazil and Uruguay tend to produce large amethyst geodes better known as amethyst cathedrals. These large geodes are typically found in small crevasses in rocks known as vugs. Since vugs are ofter formed by lava and magmatic flow, it is the ideal place for large geodes to form but they vary in color richness. These vugs are found in Minas Gerais, Rio Grande do Sul, Bahia, and Maraba, Brazil but are also found in Uruguay. Uruguay tends to produce amethyst that is of medium color purity to a deep and solid purple. Because of this, Uruguay is believed to produce the deepest purple available.
 

Vera Cruz and Guerrero, Mexico are two places that actually produce opposite types of amethyst. While Vera Cruz amethyst is lightly shaded and more often clear than purple, Guerrero amethyst tends to be a deep and solid dark purple. In the other country that borders the United States, Canada mines crystal druses in Thunder Bay. These druses are nothing more than clusters of small points, but these amethysts have a reddish tint under the surface, a color unique to Canada. Returning to Africa, the amethyst mines are located in Zambia and Nambia which are known for producing amethyst with beautiful clarity in their color. All of the deposits in the United States range in purity of color from medium to high and are found in Maine, Pennsylvania, North Carolina, South Carolina, Montana, Colorado, Georgia, Arizona, Rhode Island, and Virginia. The most notable sites in Europe are Italy and Germany. Italian amethyst has an even variety of purity while German amethyst often come out pale in color are found with other crystals like agates.
 

          While the places mentioned in the above two paragraphs are the most known places for the gemstone quality, amethyst is also found in Bolivia, Argentina, Madagascar, India, and Sri Lanka. While these five places aren’t as well known as the deposits of amethyst in Brazil, they still have mines located within their borders. Amethyst started out as a charm to ward off different things, and then turned into a piece of jewelry worn by royalty. Because of its deep purple, amethyst is still believed to represent a type of royalty within the minds of many, but, while the true abundance of the gem remains hidden, it is now considered one of the most abundant and popular gemstones in the market today.

Picture taken by April Tucker
 

Picture taken by April Tucker
 

Picture taken by April Tucker
 

Sources:

http://www.forthejoyofit.com/Joy6_Spiritual/Joy6_Amethyst_General_Info.htm
http://glimmerdream.com/gemjourneys/amethyst/history
http://www.professionaljeweler.com/archives/articles/1998/nov98/1198fys2.html
http://www.gemstoneeducation.com/Amethyst.htm
http://www.minerals.net/mineral/amethyst.aspx
http://www.colonialjewelers.com/learn/about-gemstones/amethyst/