2013年11月12日星期二

Ametrine and Citrine

At the end of my macrocrystalline quartz article featuring amethyst, I mentioned that when transparent amethyst is heated its purple through gray hues will become shades of yellow, gold, and brown. The resulting product is better known as citrine. Natural citrine obtains its bright sunny color from iron oxide and usually shows uneven color zones, can be translucent to milky, and is extremely rare; therefore almost all of the citrine on the market is actually heat-treated amethyst or smoky quartz (the subject of next week's gem profile). It doesn't matter if a yellow quartz stone is natural or if it has been heat-treated, it is still legally named "citrine."


What is Ametrine?


OK, so now I have a question for you dear reader: what happens when Mother Nature creates a truly beautiful and rare stone that is highly desirable? Answer: man finds a way to duplicate or replicate it! Such is the sad truth about the lovely, bicolor quartz that we know as ametrine. Mainly found in one location on earth, eastern Bolivia, half of this stone is violet and half is yellow-orange. Ametrine's commercial name comes from a combination of amethyst and citrine. Ametrine is also known as Bolivianite.

Although ametrine was known about by natives of the area for thousands of years, it wasn't "discovered" by modern man until a few hundred years ago. The legend of the Anahi mine tells of a Spanish conquistador who received a dowry that consisted of a grotto covered in ametrine crystals, when he was to marry Princess Anahi. At the time, Europeans were focused on finding gold and silver in the "new world," so the beautiful crystals didn't mean anything special to him. When it came time for him to return to Spain, his new bride planned to accompany him. However, her tribe wouldn't hear of their princess leaving, and plotted to kill the Spaniard. Princess Anahi learned of the plan and warned her beloved, presenting him with the ametrine crystal she wore around her neck as an amulet. It is said that the princess than went to visit their special grotto once more before leaving her country with her husband, but then she mysteriously disappeared. When the Spaniard heard what happened, he and his crew fled for their lives, only later realizing what the bicolor crystal she had given him symbolized: her love of her country and of him.

Ametrine is relatively new to today's gem world, as it didn't make its official appearance to the lapidary world until 1979 at the Tucson gem shows. Naturally-occurring ametrine is truly a work of art that lapidaries enjoy cutting and carving it into a variety of items to be used in the jewelry making world. Because it is only found in one small country, the best quality natural ametrine, that with a perfect distribution and definition of both colors, soon became more difficult to find. Scientist Dr. Kurt Nassau developed the heat treat method that is used today to produce ametrine stones with "perfect" color balance. While heating amethyst to turn part of it to citrine, occasionally a raspberry color results; if this color is rather pale, it can be called champagne quartz.

About Citrine

The name citrine comes from both the French word "citron," meaning citrus, and was most often associated with lemons and the Latin word "citrina," meaning yellow. Extremely abundant and therefore affordable, citrine carries many labels that mimic its color. Some of these, produced by heating amethyst, are: lemon yellow, canary yellow, honey, yellow-orange, and yellow-brown. If a citrine is labeled lime or yellow-gold, it is more than likely heat-treated smoky quartz (more on that next week).

I actually own a few pieces of what was sold to me as "top" citrine about 17 years ago, where the deep orange color at the bottom of the stone's pavilion flashes through the facets, giving the stone an almost glowing effect. Of course with all of the new marketing venues today, different colors of citrine have been given new, more attractive names like whiskey, cognac, champagne, and "butterscotch." (I do have to mention here, that I had never heard of butterscotch quartz before and my research found controversial notes as to whether or not this is a natural or a treated type of silica; my guess is, treated!)

Natural citrine deposits mainly of a pale yellow color are occasionally found in Brazil, Spain, Russia, France, Madagascar, Scotland, and Colorado, US. Heat-treated "amethyst" citrine can come from all over the world, as the least attractive and less vibrant purples of amethyst are chosen to turn into the more desirable citrine lapidary material, while deeper colors of amethyst are heated to create deep orange and sherry colored stones. Warning: no matter what the color, citrine will fade in bright sunlight!

Citrine can be used as the modern birthstone for those born in November. I believe this decision may have come from two sources. In the past, citrine was marketed as "gold topaz," causing citrine to be named "Brazilian Topaz" for a while and topaz is the traditional November birthstone; and one of the stones described in the Bible as having been used in Aaron's Breastplate, from which most birthstones evolved, could have been citrine. So, topaz or citrine? The easiest way to tell citrine/quartz from topaz is to gently feel each stone. Topaz will feel a bit soft and almost soapy or silky, whereas quartz will feel hard and smooth like glass.

Citrine is the anniversary stone for the 11th year of marriage. Legends tell of early Greek and Roman people associating citrine with the planet Mercury and it was believed to protect one from the venom of both a snakebite and evil thoughts and words, carrying "the power of the sun." Personally, I always have a large citrine crystal in my money bag, as citrine is known as the "merchant's stone," said to attract money and success (every little bit helps!).

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