Gem Profile 24: Diopside:  
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         A gem with the rich, saturated color, yet most gemstone information pages don’t even mention diopside.  Nonetheless, it’s a pretty gem material that, despite its odd name, can be a great addition to your” green gems” list. 

            One major reason diopside has been overlooked is that it has only recently become available in sizable commercial quantities, but now that it is available maybe it’s time to change its name.

A gem by any other name:
          Diopside is part of the pyroxene group (straight=single chain silicates), as are jadeite, spodumene, enstatite, and another dozen or so minerals with unappealing names, such as hedenbergite, and kosmochlor, which are not significant for the gem industry. 

            However, the move towards trade marking consumer-friendly labels just might make diopside a common gemstone in the color-case under names such as vertelite (Siberian chrome trademarked by Diopsidemines.com), imperial (another chrome color diospide, trademarked by Columbia Gem House), and tashmarine (Uzbekistan material, also trademarked by Columbia Gem House).

            “There is a general discontent in the marketplace about the name “chrome diopside,” says Adam David of Diopsidemines.com.  “when you show someone—says a retailer of wholesale jewelry manufacture—the gemstone, they instantly love it.  But they are a little apprehensive about what their customers will think of the name ‘chrome diopside’ for a gemstone. 

            Just a few months ago, Diopsidemines.com trademarked the name vertelite for Russian chrome diopside.  “The name was created from ‘vert’ (the root for green) and ‘lite’ (the root for stone).” Notes David

Country of origin:         
        Diopside is found all over the world in small mineralogical deposits, but sources for commercial quantities are few.  Chrome diopside is mined primarily in Siberia, in the Sakha Republic (a.k.a Yakutia).  The Yakutia territory is located in the extreme north of Asia and is considered the coldest place in Siberia as well as in the northern hemisphere.  Winter lasts for nine month, and it’s too cold to mine diopside in the winter—which makes it difficult to keep production levels steady throughout the year.  During the Siberian winter, reindeer sledding is a much more common pastime than mining. 

            Yakutia also is the source of 99% of all Russian diamonds.  Chrome diopside, which is a diamond mine indicator mineral, is sometimes found as an inclusion inside gem-quality diamonds. 

            Gem-quality diopsides not colored so much by chromium are found elsewhere, including Sri Lanka, Brazil, Madagascar, South Africa, Burma, and Pakistan.  Uzbekistan, located between Tajikistan, and Turkmenistan is becoming an important locality for the gem diopside called tashmarine.  India seems to have the major deposits or phenomenal diopsides such as cat’s eye or star diopsides.

 Color and other qualities:        
         If you like green, you will like diopside, which come in shades that range from emerald to peridot color. It can have wonderful saturated color, as does the Siberian chrome variety, and with just a splash of chrome, it’s as good as fine emerald.  With more than a splash, however, it can become too saturated and too dark.  That’s why somechrom diopsides are cut in a shallow step-cut or brilliant-cut style. 

            With a little less than a splash of chrome, as in the newly found Uzbekistan tashmarine material, the color seems less saturated and partially grayish or brownish.  This color lends itself to concave faceting, which is used to boost a lighter, less saturated color.  As a general rule, the color of the African material is more like a yellowish, peridot color.  Because of its density, a diopside gem will look bigger than a sapphire of the same weight, but smaller than an emerald of that same weight.

            On the Mohs hardness scale, diopside is ranked between 5.5 and 6.5.  Because it has a direction of perfect cleavage, similar to topaz, it’s best to cut diopside in rounded shapes (oval and round prevail).  But because of the shape of the rough, cutting into rounds and ovals can cause a gem to lose up to 90% of its rough weight.  IN other words, to get 4ct. of polished chrome diopside, you might have to start with 40ct of rough. 

            With the chrome material, it’s very hard to get clean rough in sized over 5cts. And with a possible 90% cutting weight loss, this leave a lot of melee—ideal for accent stones, earrings, and pendants.

            Quantities of both tashmarine and vertelite are making diospides commercially available for large manufacturers.  “we produces 10,000 to 15,000 carats of faceted chrome diopside per month” say David “ It’s cut mainly into calibrated sizes from 2mm up to 9mm x 7mm (approximately 2cts) WE do cut bigger stones up to 6 or 7 carats, but not in large amounts.

Enhancements: 
         Diopside has not yet been enhanced

Bench Precautions: 
        Remember the cleavage! Diopside must be handled with care. It’s also sensitive to heat, so remove or protect the gem during repair.  “It seems to be fairly tough,” says David “It’s wearability is good.  We see it used in rings and pendants.”

Care and cleaning: 
            Diopside is softer than tanzanite, so precautions for such a soft stone should be discussed with your client.  Also avoid all bleach or cleaning liquids, because the acids may dull the polish of the gem. 

Price: 
         According to Diopsidesmines.com the average price for a top-quality 9mm x7mm oval chrome currently ranges from $100/ct to $120/ct. Tashmarine have their own pricing structure since they are marketed mainly from one source and come in much larges sizes than chrome material.   

    
JCK, August 2004 
By Gary Roskin, G.G., F.G.A
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