fireforged
starting to spend too much on rocks
Member since December 2015
Posts: 215
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Post by fireforged on Jun 9, 2016 12:31:24 GMT -5
At the risk of creating a controversy, how do you identify a rock as being turquoise rather than chrysocolla or some other green/blue rock. As an example, I bought some very nice blue chrysocolla from Jeff Barnhouse. I am happy with it in every way. I do not doubt it is what he says it is. However, it sure looks like some "turquoise" I have seen. So what are the indicators you use short of sending the item to a lab?
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metalsmith
Cave Dweller
Member since October 2012
Posts: 1,537
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Post by metalsmith on Jun 9, 2016 13:28:12 GMT -5
Specific gravity: Chrys (1.9)2.0-2.2(2.4) Turq (2.3)2.6-2.8(2.9) figures outside the parentheses are those most commonly found.
Streak: Chrys: White to pale blue Turq: white
Hardness: Chrys 2-4 Turq 5-6
Refractive index; needs kit, but not a lab
HTH
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Post by adam on Jun 9, 2016 13:31:31 GMT -5
So, chrysocolla breaks easier than turquoise? Sums it up.
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fireforged
starting to spend too much on rocks
Member since December 2015
Posts: 215
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Post by fireforged on Jun 9, 2016 13:40:33 GMT -5
How about the so called "chalk" turquoise from nice hard blue chrysocolla?
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Post by orrum on Jun 9, 2016 16:45:11 GMT -5
So how do u do do a specific gravity test???
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metalsmith
Cave Dweller
Member since October 2012
Posts: 1,537
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Post by metalsmith on Jun 12, 2016 12:41:10 GMT -5
Weigh the sample Weigh the sample in water. Then there's a whole load of stuff out there on the internet that might confuse the issue. For weighing in water, the formula can be simplified to this. SG = weight when dry / (weight when dry - weight when wet) Take care not to run bubbles into the water as you pour it into its container. If you wish to be ultra-precise, use de-ionised water. Use a set of scales that is right for the problem - for example you will need to weigh single carat weight stones to the nearest 0.05 carats or better. Usually better. Repeat the test and take the average. However you'll need to be careful with beads where there may be aeration in bead-holes. For Turquoise, the SG may be variable with repeat measurement as water replaces air within the matrix - so the 'dry' weight may differ in which case it is best to go with repeat weighing whilst dry, before wetting. Then repeat weigh when wet. One of the best tests going imho.
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Post by orrum on Jun 12, 2016 21:21:13 GMT -5
Ok I gotta try this! Thanks!
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