CHEMISTRY (K,Na)(Na,Fe+3)2(Li2Fe+3)Si12O30 + Mn
CRYSTALLOGRAPHY Hexagonal, microcrystaline.
REFRACTIVE INDEX 1.607 – 1.610
HARDNESS 6 – 6.5
SPECIFIC GRAVITY 2.74, variable
HEAT SENSITIVE ?
WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS Avoid rough handling
*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on “Hardness and Wearability.”
Grape Jelly Purple, is how the color of this gem is described. In spite of the popularity of that food in the US, the gem isn’t very popular among consumers. Even sophisticated gem shoppers ignore this beautiful gem. Most sugilite sales are in Asia, very few in North America.
Sugilite was named for its discoverer, Professor Ken-ichi Sugi, a Japanese petrologist. He first discovered tiny crystals of the mineral in 1944. The location of this first discovery was the Iwagi Islet in Southwestern Japan.
The original Japanese materials were just tiny, yellow crystals with no gem value. In 1955 some dark pink crystals were found in Indias Central Province that were also identified as Sugilite. However, there were not cuttable either.
In 1975 a thin seam of Sugilite was found in a core-drill sample from a manganese mine, near Hotazel, South Africa. This material had enough manganese content to give it the deep purple coloring the gem is famous for. The deposit was small, but significant because it is the source of the first gem grade sugilite.
Exploratory mining continued and four years later a commercial sized deposit was found. It is estimated to contain as much as ten to twenty tons of sugilite. However, the deposit is 3,200 feet below the surface! With that technical limitation, combined with a small demand, most of it is still in the ground. What does come out has a high price for an opaque gem material, simply due to the difficulty of removing it from such a great depth.
So far, this is the only known deposit of gem grade sugilite. About half of it has the deep purple coloring that is considered gem grade. While almost all of it is opaque, a very tiny percentage, maybe 1/10 of 1% is translucent. Needless to say, this translucent, Sugilite Gel is extremely rare, expensive and highly prized.
When grading sugilite, the most important factor is its color with the deepest color recieving the highest grade. On close inspection you will see that the mineral is mottled. This does not effect the value, provided the overall color remains deep. If there are lighter areas, mixed in with the dark purple, then the value does begin to decline.
Sugilite is available in fairly large sizes. Gems over ten carats are common and no additional value is given to these sizes. Currently, top quality sugilite gems are wholesaling in North America for around $8 a carat. The retail price is usually between $16 and $25 a carat. The translucent sugilite isnt available in sufficient quantities for market values to be established.