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Post by 1dave on Mar 29, 2024 13:46:47 GMT -5
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Post by vegasjames on Mar 29, 2024 18:11:45 GMT -5
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Post by vegasjames on Mar 29, 2024 18:14:00 GMT -5
Rhyolites are formed from viscous, high silica lava flows They consist of feldspar and quartz making them a bit softer that quartz rocks such as chalcedonies.
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Post by rockjunquie on Mar 29, 2024 18:24:09 GMT -5
I really like rhyolites, too.
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Post by velodromed on Mar 29, 2024 19:22:54 GMT -5
I love rhyolites. They come in so many colors and patterns. Here are some examples from Nevada. .jpg" alt=" "] They tumble so nicely also. I love the ones I got from you.
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Post by liveoak on Mar 31, 2024 6:13:34 GMT -5
A perfect example of why I can't ID many rocks. So much variation.
Patty
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Post by rmf on Mar 31, 2024 7:12:51 GMT -5
vegasjames do you have names that go with the rhyolite images? Also, I did not know Goldfield Jasper ( #2 & #10 above) was a rhyolite. Thanks for the post. I am not a big rhyolites fan in general because many do not polish well but Goldfield Jasper is one of my favorites.
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dillonf
fully equipped rock polisher
Hounding and tumbling
Member since February 2022
Posts: 1,595
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Post by dillonf on Mar 31, 2024 9:42:41 GMT -5
I've always thought of rhyolites as grainey and of inconsistent hardness, but it appears I have much to learn. There are definitely some beautiful examples of rhyolites above.
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Post by vegasjames on Mar 31, 2024 17:04:25 GMT -5
vegasjames do you have names that go with the rhyolite images? Also, I did not know Goldfield Jasper ( #2 & #10 above) was a rhyolite. Thanks for the post. I am not a big rhyolites fan in general because many do not polish well but Goldfield Jasper is one of my favorites. Most the rhyolites do not have names, so I name some of them such as the fine grained multicolored ones I simply call confetti stone.
The green one took me many years to identify, and only comes from one small location not easy to access. About a mile hike up and down some very steep terrain to reach the main deposit.
Most of these rhyolites are from the Goldfield District (1, 2, 3, 8-14, 18-20). Some from the Gemfield area, but not the claim. I know several areas around Gemfield that have really nice common opal and rhyolite that is generally better quality. The material from the claim though is mainly rhyolite, known as sandstorm rhyolite or candy rhyolite, and there is some common opal, and green jasper at the claim as well.
The owners do have the material misidentified as "chalcedony". The only chalcedony at the claim is the dark green jasper. The colorful stones with flow banding is rhyolite, which gets the flow banding from the flow of the viscous lava. Chalcedonies are the dehydration product of opals and thus do not have flow banding.
These rhyolites do take an excellent polish. I water tumble them (no grit or polish) in the rotary tumbler for a month, then water polish them in the vibe tumbler for a week and they come out very glossy. I have done this with chalcedonies as well, which works, but they do not get as high of a polish. I think this is because the rhyolite is slightly softer being a mix of feldspar and quartz and so grinds a bit easier creating a smoother surface faster. I may just have to water tumble the chalcedonies longer to get more of a polish.
Here is a video of the water tumbled candy rhyolite. Water tumbling helps maintain more of the stones natural shape rather than rounding the stones, which tumbling with grit will do.
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