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Exposing Garnets

Posted by Jesse Donaldson  
Jesse Donaldson June 26, 2012 06:45PM
Hi all,

I'm looking for advice on how to best expose the garnets(?) in the attached rock.
Ideally, I'd like to remove enough of the matrix to expose buried garnets and display nicely formed crystal faces.

The matrix seems to be pretty soft (< 4), but abrasion with a rotary wire brush is still awfully slow going, and "feels like" it could damage the edges of exposed crystals. I'm not sure how to best remove the matrix without damaging the crystals. I have a few ideas, but thought I'd ask around before wrecking my specimen. smiling smiley

I'm considering:
* Sandblasting with walnut shells
* Vibratory tumbling with walnut shells
* Splitting off layers of the matrix with a chisel or knife

This came from a stream in Windsor county, Vermont, USA.

Thanks for any suggestions!
open | download - photo-2.jpg (449.3 KB)
Alfredo Petrov June 26, 2012 08:14PM
Air abrasion with glass microbeads will work much faster than walnut shell.
David Sheumack June 27, 2012 12:28AM
This video clip might give you a few ideas for preparing your specimen.
Jesse Donaldson June 27, 2012 03:22PM
Thanks for the ideas.
I'm a bit worried that sandblasting with glass beads might damage the crystal edges, but I'll give it a try if I have trouble with other methods.

The youtube video was definitely useful (although the first one that came up was about offroad vehicles -- had to go back one).
I recently picked up an old dental electro-mallet, which might be just the thing to let me delicately chisel away the matrix.

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