carleton
spending too much on rocks
Member since April 2012
Posts: 277
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Post by carleton on Sept 10, 2012 0:31:44 GMT -5
We have been meaning to get one for quite some time but it keeps getting put on the side. We purchased some bulk "facet grade" garnets, from two places actually, I quote facet grade as I think their facet "seconds" judging by the number that were cut 50% of the way and then for some reason abandoned. We were hoping to get them looked at before working too many more of them or listing them as garnets as the seller had little info on them. So if anyone is interested in getting us an RI value we would be willing to send a couple dozen or so for free. We can cut and polish one if needed. I know the basics, but if this is a low ball trade, please feel free to add a money quote or other options. I don't know the cost of RI fluid or how much is used etc... they were asking $1 or $1.50 ea for the large ones. Thanks, Carleton
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Post by geoff on Sept 10, 2012 1:48:35 GMT -5
I haven't bought one yet, otherwise I would be happy to help. Still working on completing my mineral lab.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,623
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Post by QuailRiver on Sept 10, 2012 13:09:23 GMT -5
Hello, I deal some in facet rough on a small scale. Looking at your photos I think you don't have anything to worry about. I've never heard any reports of the Rhodolite, Pyrope or Almadine varieties of garnets being misrepresented. Only the rarer varieties of Tsavorite and Spessartite.
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steveo
spending too much on rocks
Member since October 2011
Posts: 273
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Post by steveo on Sept 10, 2012 16:21:35 GMT -5
I don't have one yet either, just learning to cut, but wondering where you guys get rough? I have been getting a little at some of the shows I've gone to.
Thanks
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carleton
spending too much on rocks
Member since April 2012
Posts: 277
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Post by carleton on Sept 10, 2012 17:58:57 GMT -5
Thanks for the replies.
Quailriver, I agree and also have had no experience or heard of any with garnets, but had no experience with facet anything really. The price threw me off, I guess I expected them to cost more. I did buy a sizable amount, but when I turned him down flat on his first quote, he let me get about 100 feet away and then chased me down and cut it down by 1/3. I guess I am paranoid, lol.
Steveo, we typically get ours from dealer shows and the odd gem shop ourselves. If your looking for garnets we have some for sale ;D At least I hope we do.
Probably time to just get all the lab equipment...
Carleton
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RocknCritter
spending too much on rocks
Member since November 2008
Posts: 489
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Post by RocknCritter on Sept 10, 2012 19:04:36 GMT -5
A refractometer isn't your best tool for identifying garnets. Refractometers will read an R.I. from 1.35 to 1.80. Since garnets can vary from 1.69 (grossular) to 1.87 (uvaroite), there's a lot that may not even register on a refractometer. While it's never a good idea to give an i.d. solely on a visual appearance, it looks like what you have is either almandine (1.76-1.83) or pyrope (1.72-1.76). So the pyrope will show up. The almandine might. Think about testing with a polariscope and spectroscope also.
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carleton
spending too much on rocks
Member since April 2012
Posts: 277
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Post by carleton on Sept 10, 2012 19:10:40 GMT -5
Thank you for that extra info, I think the one kit we looked at includes all 3, I will be sure to keep that noted Carleton
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Post by geoff on Sept 10, 2012 19:17:34 GMT -5
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RocknCritter
spending too much on rocks
Member since November 2008
Posts: 489
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Post by RocknCritter on Sept 10, 2012 19:26:25 GMT -5
I had actually considered the Gem N Eye at one point except for the paragraph from their website -
"It is still not as precise or consistent as a traditional critical angle refractometer, and it does not measure birefringence. Because the Gem-n-Eye uses reflectivity to indirectly impute Refractive Index, any variability in the surface of a gem can result in some variance in your readings. On the whole, your gemstone measurements should be within about +/- .010 of an RI value."
So it seems like a great tool to use along with critical angle refractometer since you can still measure birefringence. It's also wise to use all the gemological tools and not just one to provide a positive i.d.
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RocknCritter
spending too much on rocks
Member since November 2008
Posts: 489
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Post by RocknCritter on Sept 10, 2012 19:31:17 GMT -5
I should have also mentioned testing with a dichoricscope and/or specific gravity. mikon-online.com has a portable gemological testing set that I was hoping to see in Denver later this week. I just found out that they aren't even listed in the show directory. Darn. Maybe it's an error.
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