Shall we start with blue transparent stones and how to quickly indentify them?
Name some stones here and we'll discuss diagnostics.
Let me start with Topaz, Tourmaline, Diamond, Apatite, Benitoite, Sapphire, Zircon.
Add your own ones to this list and we'll start discussing the features for fast identification.
Joined: Mon Oct 17, 2005 2:39 pm Posts: 3528 Location: San Francisco Bay Area, CA
Ok, no one's answered... but I've done a bit more poking around and it seems that beryl with the above color is being billed as irradiated. Anyone familiar with this process?
Joined: Sun Oct 16, 2005 3:36 pm Posts: 192 Location: San Francisco
There are 2 varieties of blue beryl, aquamarine and Maxixe-type.
In 1917 a variety of deep blue beryl was found in the Maxixe Mine located in the Piaui area south of Arassuahy in Minas Gerais. It was noted that after exposure to sunlight or strong artificial light that this blue beryl would fade lowly but irretrievably. The optical character of this Maxixe-type blue beryl is significantly different from aquamarine. If anyone is interested in the specifics of these differences, let me know.
In 1973 quite a few of these dark blue beryls were showing up on the market again. They had the same anomalies and similarities in optic characteristics to the Maxixe beryl. Kurt Nassau and his colleagues studied these stones and found that their color was due to irradiation and annealing, BUT they faded just like the original Maxixe beryls.
I have recently seen some darker blue beryl available, that is considerably darker in tone than one would expect with aquamarine, but I believe it to be aquamarine as opposed to Maxixe-type beryl. We have a couple pieces in the shop where I work that are similar in color to the stone that Gem-n00b posted. The locality of the material that we have in the shop is reported to be Brazil, and the vendor claims the stones to be untreated. There was a recent find of dark blue aquamarine in Canada:
Ux4 is also in possession of some dark blue stable aquamarine. Perhaps he can share a little more information on it, as to locality and treatment if known.
_________________ "Do well and you will have no need for ancestors" Voltaire
Joined: Sun Oct 16, 2005 3:36 pm Posts: 192 Location: San Francisco
Sometimes I'm silly!
Dichroism: Aquamarine: deeper color belongs to the extraordinary ray
Maxixe: deeper color is found belonging to the ordinary ray, while the extraordinary ray is almost colorless
Spectrum: Maxixe: Strong absorption in the red end of the spectrum (695, 655nm, with weaker bands showing at 628, 615, 581, & 550nm.) (somewhat like zircon!)
Habit and chemistry: The original maxixe stones exhibited little crystal form, and had high contents of caesium & boron.
Specific gravity: Maxixe: 2.80
Aquamarine:2.65-2.76
Joined: Mon Oct 17, 2005 2:39 pm Posts: 3528 Location: San Francisco Bay Area, CA
What kind of fading is noted with these Maxixe-types? Are we talking fading to the color of an aquamarine? Fading to goshenite? Fading to a still-deep-blue-but-not-quite-as-deep-blue-as-before?
Joined: Sun Oct 16, 2005 3:36 pm Posts: 192 Location: San Francisco
The picture that is used in the above article was taken from the Winter 1998 Issue of G&G, which features a 1 page story on Maxixe beryl that was submitted to their lab for testing.
If anyone is interested in seeing the G&G article, send me a PM.
_________________ "Do well and you will have no need for ancestors" Voltaire
Users browsing this forum: No registered users and 2 guests
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum