Lapidaryforum.net
Rock Art => Knife Making => Topic started by: VegasJames on October 28, 2018, 01:56:38 PM
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Have not made a positive ID on this material yet. Will be sending it in shortly for testing. It is very hard. Cannot scratch is with a pure quartz crystal but I was able to make a tiny scratch in the quartz crystal with it. The color varies from light green to dark green and even dark blue-green. There is traces of turquoise running through some of the material.
(https://farm5.staticflickr.com/4431/36897638881_9316a4b34f_c.jpg) (https://flic.kr/p/Ydw3xB)DSC_0803 (https://flic.kr/p/Ydw3xB) by James Sloane (https://www.flickr.com/photos/143011703@N05/), on Flickr
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If it is really tough it may be peridotite or an associated pyroxene mix.
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If it is really tough it may be peridotite or an associated pyroxene mix.
Thanks. I checked the hardness of peridotites though and they area hardness of only 5.5 to 6. This has a hardness of around 7 as quartz will not scratch it but it can barely scratch a quartz crystal.
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Has an almost rainforest jasper look to it. Please let us know what the outcome is when you have it tested.
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Has an almost rainforest jasper look to it. Please let us know what the outcome is when you have it tested.
Hopefully I will be sending it off to GIA shortly. I need to make a small ca if it under 20 carats. Normally I do mot do small cabs since I dom't use a dop stick. A soon as I can get that done and make a couple of cabs of suspected turquoise to send off I will get them off to GIA.
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lapilli metatuff ?
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lapilli metatuff ?
No idea. I did send it off for XRD testing in New Mexico. They came back with 50% quartz and 50% sanidine, which makes no sense since the 50% sanidine would reduce hardness. Sanidine is only a hardness of 6 and brittle. This stone can scratch a quartz crystal and is not brittle at all.
Of course this is the same lab that I had some turquoise blue stones tested and they came back with 100% malachite on two of the stones and 98% malachite and 2% quartz on the third. Since malachite does not occur in blue I have serious doubts about their testing or I have the rarest malachite on Earth.
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If the sanidine sorce was volcanic like a rhyolite it very well could be a tuff. We have lots of them in the northwest but it also looks more than a bit like a local very rare rock keratophyre with a very similar structure and color.
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If the sanidine sorce was volcanic like a rhyolite it very well could be a tuff. We have lots of them in the northwest but it also looks more than a bit like a local very rare rock keratophyre with a very similar structure and color.
A tuff would not have a hardness of 7+.
How about the keratophyre. Is it at least a 7 in hardness?
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Tuff is a strange beast.You can carve many tuffs with your fingernail but in 40 years of cutting the hardest stone I ever found was a piece of tuff below Glacier peak. It had an open structure and with magnification almost resembled a cheese grater in texture.As for hardness it was off the charts harder than any chert or porcelain jasper I have ever cut and noticeably so.I think geology makes weirder things at times than we can imagine.