Sugilite: Purple Pleasure

by delpfinewelch on June 29, 2009

If you like purple, you’ll like sugilite. 

The color of sugilite ranges from pale lavender to a deep purple.  Pure purple–with no impurities–and translucent, is the most valued and is considered gem grade.  Gem grade is the most expensive and the most rare.  Gem grade sugilite is also known under the trade names of “Royal Lavulite” and “Royal Azel.”

Sugilite is relatively rare and relatively new.  It was found first in Japan in intrusive igneous rock in 1944 by Ken-ichi Sugi and named for him.  A large deposit was discovered in South Africa in 1975 in a metamorphosed manganese deposit.  Four years later, another deposit was found 3200 ft below the original.  It has also been reported from Canada, India, Italy, and Australia.  

The chemical formula of sugilite is KNa2(Fe,Mn,Al)2Li3Si12O30.  It has a hardness of 5.5 to 6.5 on the Mohs scale.

Like so many other minerals, sugilite often contains black matrix.  That’s true of my stash of sugilite rough.  Not gem grade, but beautiful nonetheless.  Actually, I think that the strings of black matrix give it character. 

Here are some photos of jewelry that I’ve made featuring sugilite cabochons that I’ve cut:

Sterling silver woven wire necklace with clasp featuring a sugilite cabochon

Sterling silver woven wire necklace with clasp featuring a sugilite cabochon.

Sterling silver pin with sugilite cabochon and cobaltocalcite drusy.

Sterling silver pin with sugilite cabochon and cobaltocalcite drusy.

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delpfinewelch

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Chrysocolla: A blue-green beauty

by delpfinewelch on February 17, 2009

Chrysocolla is one of my favorite gemstones.  It has a beautiful blue-green color, sometimes more blue, sometimes more green.  Some of the different colors are due to inclusions of azurite (blue) or malachite (green).  Like azurite and malachite, chrysocolla is a copper mineral.  Chrysocolla is often confused with turquoise.  You may also see the term “parrot-wing” associated with chrysocolla.

Pure chrysocolla is quite soft — 2.5 to 3.5 on the Mohs hardness scale.  If more quartz is present, then the hardness increases, making it possible to cut stones and beads for jewelry.  Chrysocolla is typically cryptocrystalline.  Often, beads and commercial cabochons are stabilized.

Chrysocolla, azurite, malachite, and turquoise all form from the weathering of copper deposits.  Chrysocolla is a hydrated copper silicate with the formula (Cu,Al)2H2Si2O5(OH)4.nH20.  Azurite and malachite are copper carbonates.  Turquoise is a copper phosphate.

Chrysocolla is found all over the world in association with copper deposits.  In the US, localities exist in Arizona, New Mexico, and Utah.  Outside the US, chrysocolla can be found in Russia, Slovakia, Israel, Democratic Republic of the Congo (Zaire), Mexico, Chile, and Australia.  It is usually found as a crust, filling veins, or as a botyroidal mass.  Chrysocolla is a secondary mineral and often replaces earlier forming secondary minerals.

Chrysocolla is considered to be gem grade when it is translucent and a single color.  Personally, I like the opaque chrysocolla with all its “impurities.”  I have purchased small amounts of chrysocolla rough at local gem shows from San Juan Gems.  I purchased a large amount of rough from Village Silversmiths.

I cut and polish the rough to make cabochons to include in my jewelry.  Here’s photos of some of my pieces with chrysocolla cabs as the focal point.  See my Etsy shop for more photos.

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