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 Post subject: Identifying today's "exotic" garnets...
PostPosted: Wed Jul 15, 2020 11:37 pm 
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Here is a question for you gemologist/appraisers...

In my pursuit of facet rough, these days I am faced with a plethora of new orange - red - purple garnet "varieties".

Marketing names such as Umbalite, Lotus, Imperial, Mahenge, Umba, Malaya, and lots of others (like Cayenne, Cherry, Grape, etc.)

Rough prices for some of these (like Rose Almandite) are start at `$1.00/ct. Others like Mahenge and Imperial may go up to $60/ct and (much!) more.

The question... :?:

In the future after the (finished) gem and its marketing claims are long seperated, will it be possible to identify the pricey garnets from the more common? Or are these names more marketing hype to help the seller get a bigger price? I don't see any listings in the Gemguide for the sexy-named types...

*********************

A friend recently received a 25 ct rough "Mahenge" piece, supposedly worth $45/ct. Small black inclusion on one side as I have seen in the rough before. In dopping, it broke from the heat at the inclusion, in to 4 pieces from 3 ct to 7 1/2 ct. Disgusted, he gave it all to me, saying "I don't cut little stuff.

I cut the smaller piece in to a 1 ct trillion. Showed it to a gemologist, who tested and said "Rhodolite." RI was right on. So either the friend was scammed, or Mahenge is just a glorified rhodolite.(?).

Just wondering...

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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 11:04 am 
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One must really understand the Garnet Group to get an idea for what is happening with Garnets these days.

As far as gem Garnets go there are two types the aluminum, and the calcium based.

The standard end members of the group in the Aluminum are Pyrope, Almandine, Spessartite. Since basically all Garnets of the aluminum group are actually mixtures of the end members in various proportions it is even hard to get agreement of when to call a stone Pyrope, Almandine, or Spessartine. I have heard some say that if the garnet is composed of more than 50% of an end member it should be called that. Others have said that it must contain 70% or more of an end member.

Most of the "marketing names" you mentioned are either the Pyrope - Almandine or Pyrope - Spessartine mixtures. None of these really have a mineralogically defined proportion ratio. Names like "Malaya" (pyrope spessartine) have some history based color. Some of the new names like Mahenge imply a location that produced Garnets that tended to be of a certain tone, and hue. However, the origin data is not well developed so there is no reliable way to determine origin. I have been "in the room" when some of these namings have happened. It is pure marketing, not gemology.

A friend of mine Kirk Feral has done some good work estimating the composition of Garnets and classifying them based on refractive index and magnetic response. It only really deals with the end members, and Malaya. All these new marketing names are not included.

https://www.gemstonemagnetism.com/under ... etism.html

The Calcium Garnets are not quite the wild west that the Aluminum Garnets are. The names these are traded under are generally the long accepted historical varieties such as Uvarovite, Andradite, Demantoid, Topazolite, Grossular, Hessonite, Tsavorite, Merelani Mint. In this set of Garnets the difference between Tsavorite, and Merelani Mint Garnets, a distinction only based on color/tone, is one of the principle grey areas.


So to answer your question. No, there are no widely accepted (or documented) gemological distinctions for most of the new Garnet names. Especially so in the Pyrope - Spessartine stones. Many just say, yeah but I know the difference when I see the stone. My take is that it mostly depends on how the stone looks, and how good a salesman you are. As you have noted, there is a wide range of price consequence involved in these rather arbitrary descriptions of Garnets.

To me, the rationale for having these marketing names is separate some of the recently found Garnets from the traditional garnets. Most of the traditional Garnets tended to be over dark, with strong modifiers of grey and browns, and very inexpensive While many of these newer garnets are much more open in color (lighter tone), and in unique, and much more attractive hues. These are much more attractive, and more rare in occurrence. They deserve to be priced much higher.

But you won't get the deserved higher price by trying to sell a "Pyrope-Almandine-Spessartine Garnet in a brilliant medium light pink/orange color" to the public. You are much better off selling a "new rare Garnet from an exotic African deposit called Mahenge that has a unique and special combination of color and brilliance.

Taking the example of the "Mahenge" rough. Both Rhodolite and Mahenge are Pyrope-Almandine mixes. A so would test in the same range on standard gemology equipment. Rhodolite is described in traditional gemology as have a strong purple component. This is how you make the variety call. Mahenge in the trade also implies both a range of color tone and Hue . So, it is in that respect just as valid a distinction and naming criteria. It could also imply a place of origin. But that I think is less critical as it cannot be proven or even judged. So, the primary difference in validity between calling a stone Rhodolite or Mahenge is that Rhodolite has a longer history of a color based name.

Hope this is of at least some help to you.


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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 7:13 pm 
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What he said ↑


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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 8:06 pm 
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Thank you for your helpful reply!

Now if you want an interesting twist...

Back in 1980's I purchased a sizable parcel of rhodolite garnet.

Along with the normal purplish red, there were a few light-medium pink pieces, cutting up to 5 carats. They hadn't started calling it anything special yet so the paler pieces just came with the rest.

Also, they had snuck in a number of pieces with an undesirable color, going from a nice magenta to a weird brownish green... No one wanted that last type at the time, so they had salted the parcel with some "trash" to get rid of it.

Moving forward to today, I need to look thru my old reject rough and see if I can find that color-change garnet!

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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 8:40 pm 
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Remember the original rhodolites from NC are light and open in color, not dark purple as the name was later expanded to include.
Mahenge is not a variety, it's just a locale known for producing fine garnets in the pyralspite family, including rhodolite, malaya and 'pastel pyrope' (not sure if that counts as a real varoety anyway). I think the bright open pinks and oranges speak for themselves in terms of value. The ones that are just high quality but mundane rhodolites as you'd get from any number of deposits (ie 'umbalite') are imo trading on hype atm. They sure bring the look of a mixed parcel together though.
The upshot is that the long-term value will probably track with appearance more than anything else, since there's no way to actually establish locale.

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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 9:14 pm 
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Stephen,
I still don't get how Rhodolite is a variety and Mahenge is not. As you said, although you can pinpoint Mahenge on a map, you cannot definitively say a garnet is from there. These days in Arusha, pyralspite garnets from all over are consolidated into "Mahenge" parcels because they fall within a certain color, tone range.

My understanding is that variety within the Garnet group is defined by color, as it is with so many gem species. The only thing that seems to matter is that it gets broad market acceptance. This includes Rhodolite. How much purple does a Rhodolite need to have? At what point does it get too purple and become a "Grape" Garnet?

Is Malaya also not a garnet variety?

How about Tsavorite, a defined color that was named by Campbell and Tiffany as a marketing name inspired by the Tsavo Game park near the Bridges Scorpion mine. It is actually coming from many locations.

How about Merelani Mint, a lighter version of Tsavorite that comes from many locations these days.

How about "Fanta" Spessartite?

This whole garnet family naming is marketing based. It seems to currently be the Wild West where people are coming up with new names to define small nuances in color differences.


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 Post subject: Re: Identifying today's "exotic" garnets...
PostPosted: Thu Jul 16, 2020 9:32 pm 
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1bwana1 wrote:
Stephen,
I still don't get how Rhodolite is a variety and Mahenge is not. As you said, although you can pinpoint Mahenge on a map, you cannot definitively say a garnet is from there.

I take that stance since it doesn't have any strong color definition (ie, even initially it included way too wide a range to be reasonably defined as a 'variety' imo, unless we want to include every pink, purple and orange pyralspite), and only includes examples of a few different already-defined varieties, nothing that's actually new. The only real uniting factor is where they're (allegedly) from, and a tendency for high quality.

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