"Tanga" Garnet

[Gem Lover]

Quick question for the experts. What exactly is tanga garnet? Is it the same as rhodolite, just from a specific place? I''ve seen several stones that are quite expensive. I''ve been researching the different types of garnet and am pretty confused. Some of them seem so similar and I don''t understand why they have so many different names. I''d like to collect as many species as I can afford. So far I''ve got spessartite, tsavorite, tanga, hessonite, and pyrope. Thanks for any insight.

Jess

 

[jeffwhite]

You are correct. Tanga is not an actual garnet species (like spessartite, pyrope, etc.) or even a "mixture" variety (like rhodolite)... Tanga is actually just a location (in Tanzania). Most "Tanga Garnet" that I've seen is rhodolite or umbalite.

One of the things that makes the study of garnets so confusing (yet fun) is the huge number of combinations possible. Some are pure species - such as spessartite, grossular, pyrope, almandine, etc. Others are actually mixtures of some of the pure species. For example, rhodolite is a mixture of pyrope and almandine garnets. You can kinda think of it like pure metals vs. alloys.

Hope this helps!!

 

[Gem Lover]

Thank you Jeff. That helps a lot, actually. I''ve got quite a bit to learn! Are you the same Jeff White who cuts gorgeous gems? If so, how about cutting several hundred more asscher grossular''s

?

Jessica

 

[Richard M.]

Date: 5/2/2008 10:21:12 AM
Author: jeffwhite
Most ''Tanga Garnet'' that I''ve seen is rhodolite or umbalite.

Umbalite is rhodolite too, Jeff. Tanga and Umba are locations in Tanzania where garnet is found and those place-names have been attached to specific hues of the local rhodolite garnet. As you know, rhodolite isn''t really a specific kind of garnet either. It''s an intermediate blend of the pyrope and almandine species and can vary tremendously in hue and tone depending on the proportions of the two main garnet species and the presence of other garnet types.

When there is more almandine than pyrope it tends toward the purple. With more pyrope than almandine, the hue is more red or sometimes a lovely lavender-pink. Because most dealers really aren''t equipped to analyze the exact type of garnet they''re selling, they tend to invent marketing names. The names usually describe the color (i.e., Raspberry Rhodolite or Grape Garnet, both rhodolites) or the location where the stone is found. With so many names describing essentially the same thing, no wonder the public is confused!

I began studying and working with garnets over 10 years ago for the reasons you mention: the wide range of beautiful colors and the fact that, as yet, there are no known treatments for garnets except mild heating of some demantoids to purify the green color.

 

[Gem Lover]

Thank you, Richard. They are very interesting gemstones. I''m drawn to them because they are mostly untreated and come in such an amazing variety. Plus it''s my birthstone. Is there a color of rhodolite that is more desireable in the market? Obviously personal preference plays a role, but for collecting purposes is there a color that has more value?

Jess

 

[Richard M.]

Date: 5/2/2008 11:54:35 AM
Author: Gem Lover
Obviously personal preference plays a role, but for collecting purposes is there a color that has more value?


Jess

The Gem Guide, which tracks wholesale prices of colored stones, puts essentially the same values on pyrope-almandines with the following hues: slightly purplish-red, strongly purplish-red, purple-red, reddish purple, purple. It also points out that these stones are GIA Type II meaning lighter tones or large stones may not be eye clean.

Supply, clarity and quality of cut definitely affect prices, as does size. In the long run I think beauty is in the eye of the beholder, and my own eye is drawn to stones that exhibit a strongly purplish red hue. Fine ones that aren''t dark are quite scarce. But I''m also drawn to the lighter tones of violet-red. I am very fickle when it comes to beauty. Collect what your heart dictates. Garnet collectors never run out of choices!

 

[Pandora II]

I LOVE garnets.

I just had lots of fun with the whole isomorphic replacement in garnet thing in my last FGA assignment.

My tutor sent me a fantastic diagram which I''ll copy out and post up as it''s quite enlightening on how many possibilities there are.

 

[Gypsy]

I love garnets too. Most the the gemstones are own are garnets (actually, I think topaz might be catching up... I''ve been indulging a little). But it''s gorgeous and affordable. And when it''s well cut! WOW.

I''d personally love a bright red garnet... a little orange in there. SO that it''s a red... but an orangy red. YUM!