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What is the dark green gemmy material in the center of the specimen?

Posted by Timothy Bonura  
What is the dark green gemmy material in the center of the specimen?
July 03, 2012 12:36AM
Hello,
I found what I think is a Serpentine specimen a couple years ago - gemmy side down in the Rock River, downstream from the Adams Hill Nickel prospect, in southeastern Vermont. It happened to be a sunny day and I knew I had something of some significance, at least to me. So I decided to polish it with my orbital sander, working my way up with finer grits and then some automotive chrome polish. I know there is asbestos present in serpentine, so I took proper safety precautions. My question is: what is the gem-like material in the center of the specimen - when tilted, different structures (or bands) are highlighted depending on the angle of tilt - a "holographic" effect is produced. Thanks for your helpgrinning smiley



Edited 1 time(s). Last edit at 07/03/2012 12:39AM by Timothy Bonura.
Attachments:
open | download - P1030018 - 2.jpg (30.8 KB)
Re: What is the dark green gemmy material in the center of the specimen?
July 03, 2012 04:05AM
Tim,
Can we get a larger picture, and maybe several angles? I think that would generate more responses.
Thanks.
Re: What is the dark green gemmy material in the center of the specimen?
July 03, 2012 09:14PM
Here are some better photos - I hope these are helpful. Thanks!
Attachments:
open | download - P1020834 - 2.jpg (182.1 KB)
open | download - P1020835 - 2.jpg (209 KB)
open | download - P1030018 - 3.jpg (380.4 KB)
avatar Re: What is the dark green gemmy material in the center of the specimen?
July 03, 2012 11:07PM
Timothy,
Have you conducted any sort of diagnostic testing yet such as hardness, streak, specific gravity, etc...? That might also give you (and us) a better idea of what you have. My initial thought is that if you used an orbital grinder to polish it, it is likely harder than just serpentine alone but is a metamorphic rock called serpentinite, which contains serpentine minerals.
Re: What is the dark green gemmy material in the center of the specimen?
July 06, 2012 12:21AM
Dear All, After further research I've narrowed it down to Bowenite a variety of Antigorite. Thank you again. Timothy Bonura
avatar Re: What is the dark green gemmy material in the center of the specimen?
July 06, 2012 10:56AM
    
Please be aware that the various serpentine group minerals cannot be distinguished by visual means. There may be good reasons to assume that it is bowenite (you probably checked what has been published about the locality where it was found), but until it is confirmed by an appropriate analysis, it remains an assumption.
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