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Post by liveoak on Aug 19, 2022 9:37:53 GMT -5
I have a real mystery rock - 2 the same in fact.
The rock is bluish grainy sort of color, with a lavender band, and a gray weathered surface.
The interesting thing are the silvery crystals inside.
If you look at the close up photo the band above the lavender is full of very tiny ones & then there are some larger ones in the blue interior.
The crystals are square, from what I can tell & quite hard , I think the crystal & the rock are about Mohs 7.
When I first saw them, I thought, oh it's just mica -- definitely NOT mica.
Any clues ?
Thanks,
Patty
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Post by mohs on Aug 19, 2022 9:50:37 GMT -5
interesting Patty
would imagine that the host rock is volcanic perhaps andesite that had some low level metamorphism occur in a hydrothermal active area
know where it was found...
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Post by liveoak on Aug 19, 2022 9:56:21 GMT -5
So the more I investigate I'm thinking the inclusions must be pyrite.
It seems more silver colored to me than I would think, but the square crystals & the hardness are more of a give away.
Any idea what the rock is ?
Patty
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Post by liveoak on Aug 19, 2022 9:58:29 GMT -5
Interesting mohs, unfortunately no idea it's origin, I purchased a "grab bag" box & it was one of the treasures I found. Pretty sure the crystals must be pyrite, but the rest of it, no idea. Patty
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Post by mohs on Aug 19, 2022 10:05:29 GMT -5
was thinking pyrite butte was hoping gold for ya that why wondering the location that lavender would have a geologically interesting explanation
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Post by liveoak on Aug 19, 2022 19:45:45 GMT -5
I’m just guessing here, the rock could be altered limestone, dolostone, or marble. The weathered tan/white areas look like calcite, that’s what has me thinking it’s something similar. My problem with the guesses is that I believe they are all soft & the rock is likely mohs 7. I like mohs guess on volcanic , except that the crystals that form in that are feldspar & that's way soft.
No matter what it is, I thing it might make some interesting cabs- so I'm looking forward to slabbing it.
Patty
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Post by liveoak on Aug 20, 2022 6:11:55 GMT -5
Limestone, dolostone, and marble are soft, but when they become chemically altered by metasomatism/hydrothermal metamorphism that can change. Lapis is formed in this way, and has a hardness of 5-6. I'm not going to begin to tell you I understand geology enough to grasp that, so I'll have to say, Maybe.
However, if this is so , would the square crystals we guessed as pyrite form in such an environment ?
Patty
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Post by liveoak on Aug 21, 2022 5:57:16 GMT -5
Pyrite does form in these environments. Read up on the formation of skarn deposits when you have some spare time, better explained when written by experts lol! Thank you Bryon, I will.
Patty
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quartzilla
Cave Dweller
Member since April 2020
Posts: 1,208
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Post by quartzilla on Aug 21, 2022 8:09:37 GMT -5
The square crystals def look like pyrite.
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