Sugilite is a material that =was discovered in Africa about 1944 or
there about it is a pain in the neck to polish due to the natural
cleavage, although not as bad as Charoite. Here is more scientific
info on it, also it has now become nearly extinct save for old stock
Chemistry: KNa2Li3(Fe, Mn, Al)2Si12O30, Potassium Sodium Lithium Iron
Manganese Aluminum Silicate.
Group: Milarite - Osumilite
Uses: As an ornamental and semi-precious stone used in jewelry and as a
Sugilite is a somewhat obscure mineral named for the Japanese
geologist who discovered the first specimens in 1944, Ken-ichi Sugi.
It is becoming very popular in the jewelry trade. It does not form
well shaped crystals but is usually massive. This is OK, as it is
used mostly for ornamental and semiprecious stone purposes. It has a
very distinctive opaque purple color when found in its most desirable
color shades. The polished stones are mostly opaque with an almost
waxy luster and a deep reddish purple color. It has been described as
a purple turquoise although there is no relation between the two
minerals. Its jewelry uses are becoming widespread and sugilite is
being used in jewelry styles with turquoise, malachite and coral.
Some sugilite has been cut into but these are very rare.
The primary structural unit of sugilite is a most unusual double
ring, with a formula of Si12O30. Normal rings of cyclosilicates are
composed of six silicate tetrahedrons; Si6O18. The double ring is
made of two normal rings that are linked together by sharing six
oxygens, one from each tetrahedron in each six membered ring (notice
the loss of six oxygens in the double ring formula). The structure is
analogous to the dual wheels of a tractor trailer and is shared by
other members of the Milarite - Osumilite Group.
Hope this helps, Way back when I think it was around 1980 I bought
several pounds at a show and was able to pull out nearly 40 CTs Of
Jelly Sugilite. I have no Idea what that would be worth now, But my
wife has a very pretty faceted 12 CT. pendant from that rare find,
Last I had heard Just plain AA (what ever that means) was selling for
3.50 per gram in rough.
Purple Spondilous (spiny) oyster looks as good and is a lot easier
to cut and polish, Be very careful going for your final polish as the
surface spaulls quite easy