Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I am usually just a mere constituent of a gem that has been revered for over 3000 years.
I am cool as a cucumber on my own!
Nothing, and I mean nothing , can get me fired up!
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Great guess, Doos, but incorrect.
Additional Hints: My color can vary from dark green to light green due to the presence of ferrous iron. I have 2 directions of cleavage and I'm a softy at heart, but tough when I need to be.
I'm not proud of it, but I am a member of a group. I often stand out because of an absorption line at 503nm.
PS. Does it look like I'm trying to show off the new smilies in the View More Emoticon Section? I'm Shameless.
Last edited by Barbra Voltaire, FGG on Sun Jul 02, 2006 3:54 pm, edited 2 times in total.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Sorry, cmw
Another clue:
The group that our mystery stone belongs to is arbitrarily defined by the amount of iron present. Isomorphic replacement of iron and magnesium.
Habit: Aggregates of long, often fibrous (or asbestiform ) prismatic crystals
This clue should be a slam dunk!
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
We have a winner
It is a cabochon of chatoyant actinolite that was sold to me years ago as chatoyant nephrite.
Actinolite is considered a primary constituent of nephrite.
It has a hardness of 5.5 although it's fibrous structure, when chatoyant, makes it a toughie.
It is a member of the Actinolite-Tremolite series, classified as amphibole inosilicates, a series that also includes nephrite.
Its long fibrous crystals can be spun into fireproofing asbestos.
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
Where do your spectrum data come from Barbra? (See, I'm getting on board)
I checked Anderson & Payne and they describe a vague band in the yellow of "undetermined wavelength," and two faint and narrow bands at 510 and 495 nm.
They add this interesting info: "Actinolite can be thought of itself as a true jade, since 'nephrite' is merely the term for a massive amphibole of the tremolite-actinolite series. 'Mutton-fat' nephrite is almost entirely iron-free tremolite, while the commoner green nephrite contains iron and is nearer to actinolite in composition. In recent years actinolite cat's-eyes from Taiwan have been sold as nephrite cat's-eyes." So maybe your stone is really nephrite
Somewhere over the years I've also heard that chatoyant actinolite also comes from the huge nephrite deposits in Alaska.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
The inspiration for the spectrum is courtesy of
Tables of Gemstone Identification or
Bestimmungstabellan fur Edelstein Synthesen Imitationen Mit Farbigen Spektren Zweisprachig by Birgit Gunther (although the spectrum is a PhotoShop mock-up)
The 503nm reference is also in Gems by Webster. It is also almost identical to the spectrum my actinolite cab, pictured above, displays with my OPL.
I am speculating that the difference between nephrite and the more common actinolite is structural. As I recall, nephrite has an alpha helix atomic structure (with a much finer grain), which makes it harder and much tougher than commonly fibrous and granular actinolite. And, I don't believe nephrite is used for the production of asbestos.
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