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Sentient-Aberration In reply to bmah [2016-09-26 18:51:14 +0000 UTC]

That's exactly what I thought when I had this up on my previous page. I've since seen some specimens of Grossular in a lab for a course I'm taking now, though, and the color is all wrong (they were bright green). Then again, this is a highly variable mineral, and you make a great point about the chemical testing. I'd essentially have to determine if Magnesium is the culprit here. There are definitely red variants of Grossular, but this particular hue and crystal habit seems to appear more in the Pyrope variant, from what I've seen so far.

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bmah In reply to Sentient-Aberration [2016-09-26 20:55:39 +0000 UTC]

Sadly color and crystal structure means almost jack when it comes to garnets. A better determinant is the associated minerals and the host matrix - in other words, the geochemistry in context. If the garnet was part of a calc-silicate assemblage such as tremolite, then the calcium in those minerals would more likely point to grossular garnets. If the garnet is amongst a biotite schist, then the iron from the biotite mica would imply the association of almandine garnets. Pyrope and almandine are next to impossible to visually differentiate. Grossular garnets can come in all sorts of colors - green, pink, orange, white, yellow, etc.

If I was to make a visual guess then it looks like you might have "raspberry" grossular garnet, possibly from Mexico.

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Sentient-Aberration In reply to bmah [2016-09-27 00:08:20 +0000 UTC]

The matrix appears to be Dolomite. Furthermore, it appears to be a magnesium-poor dolomite.

I've also found what I believe to be specimens from the same mine or area online that are being identified as Grossular. You've got a good eye for these. Nice work  

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Sentient-Aberration In reply to bmah [2016-09-26 23:58:24 +0000 UTC]

It is from Mexico, I do believe. And it would appear that it may be in a dolomite or calcite matrix, in which case I'd certainly have to agree with the Grossular argument. I'll test the specimen here, when I get the chance.

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bmah In reply to Sentient-Aberration [2016-09-27 00:28:53 +0000 UTC]

I think your garnet specimen comes from an area around Sierra de la Cruz. This link here also has a very interesting story (in addition to pictures) on the locality: www.mindat.org/loc-7766.html

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Sentient-Aberration In reply to bmah [2016-09-27 00:38:10 +0000 UTC]

Given that this one has the incorrect Lake Jaco identification tag in the bottom of the box I store it in, I'm pretty sure you're exactly right.

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