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Post by fernwood on Jan 24, 2019 6:27:24 GMT -5
From NM or AZ. Purchased in 1980’s, Gallup, NM. Is this Onyx or Jasper? Any location ideas? Would it be worth slabbing? Thinking of getting the end with crystals sliced of as a specimen. Then slices of the rest. The red and black areas are harder than the yellow/brown ones on the edges. Yellow next to red/black areas is the same hardness as them. It split in half while on deck over winter. Thank you. 1 all close 3 close 2 close 1 Bottom of one piece. bottom Nice crystals. close 4
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Post by fernwood on Jan 24, 2019 8:22:08 GMT -5
Most of the other pieces purchased at the same time are Onyx. They are all most softer than this one.
The green areas are algae, not the actual color. The black areas are slightly magnetic. The red/black areas have a hardness of about 7 to 7.5. The yellow/brown ones on the edges are about 6.5 to 7.
Could it be a combo of Onyx, Jasper and Quartz? Plus something else in the black areas. The purple area at the bottom of last photo appears to be Quartzite.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Jan 24, 2019 11:28:06 GMT -5
Fernwood, I don't think it is either jasper or onyx. There is quartz but no micro crystalline quartz that I can see/tell. This could be oxide stained sandstone possibly, tough to say. I think dry photos would be helpful. It is an interesting piece.
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Post by fernwood on Jan 24, 2019 12:23:30 GMT -5
Interesting. It seems too hard to be sandstone.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Jan 24, 2019 14:09:50 GMT -5
It could be at a stage of metamorphism into quartzite to be that hard in areas. Jasper and Onyx would also show conchoidal fracture patterns, I dont see any in the photos. Interesting that it cracked in half out in the cold.
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Post by stephan on Jan 24, 2019 22:50:53 GMT -5
By onyx, I assume you mean “cave onyx” type material, which is calcite. True onyx is a type of agate with parallel black and white bands, which this clearly isn’t. If you have a hardness of 7+ and those colors, I’d say jasper is your best bet.
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Post by pauls on Jan 25, 2019 2:55:51 GMT -5
I agree, not Onyx the calcite or agate type. I would say it's a pretty nice piece of Jasper.
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Post by fernwood on Jan 25, 2019 3:48:26 GMT -5
Thanks everyone. I was mystified that it cracked outside as well. There were no cracks in the stone where it split.
Could it be a mix of materials?
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Post by toiv0 on Jan 25, 2019 5:22:31 GMT -5
Thanks everyone. I was mystified that it cracked outside as well. There were no cracks in the stone where it split. Could it be a mix of materials? If it cracked in the cold it probably had a small fracture with some moisture in it. When it froze moisture expanded and finished the job. Nature at work. I am not sure it is a jasper by the way the chips look and it looks sugary. Try polishing as small corner with your dremel.
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Post by fernwood on Jan 25, 2019 5:40:59 GMT -5
toiv0 Thanks. When it warms up, I will try. The red/black areas reminded me of the Mary Ellen I got from you. Placed that next to it and the texture/appearance in those areas is about the same. That made me think jasper. The white/yellow/brown areas on the edges are kind of sugary.
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Post by stephan on Jan 25, 2019 8:49:10 GMT -5
toiv0 Thanks. When it warms up, I will try. The red/black areas reminded me of the Mary Ellen I got from you. Placed that next to it and the texture/appearance in those areas is about the same. That made me think jasper. The white/yellow/brown areas on the edges are kind of sugary. I've seen the sugary areas with brecciated Jasper before, in areas where the healing material is granular or druzy. Also, sometimes what you see on the surface changes in a fraction of an inch. Finally, I think that the conchoidal fracture occurs manly when a concentrated strikes it. If the stone has previously broken by some other mechanism (such as freeze-fracture), a different appearance at the cleavage site is certainly possible.
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Post by stephan on Jan 25, 2019 9:37:14 GMT -5
If the hardness and graininess hold throughout the stone, maybe rhyolite?
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Post by toiv0 on Jan 25, 2019 9:50:58 GMT -5
Is this a rock from your field?
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Post by fernwood on Jan 25, 2019 14:36:48 GMT -5
No, not fields. Purchased in Gallup NM in the 80's.
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vwfence
has rocks in the head
Member since January 2013
Posts: 557
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Post by vwfence on Jan 25, 2019 15:35:42 GMT -5
try a drop of vinegar on a corner of it and see if it fizz's
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vwfence
has rocks in the head
Member since January 2013
Posts: 557
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Post by vwfence on Jan 25, 2019 15:57:27 GMT -5
Can you take a picture of where it fractured ?
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Post by beefjello on Jan 25, 2019 19:16:14 GMT -5
Yeah I've seen this stuff quite a bit here in AZ. Definitely a travertine/calcite 'onyx'. I bet AzRockGeek Tim knows where it's from. Here's a chunk I have and the top/bottom with crystals
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vwfence
has rocks in the head
Member since January 2013
Posts: 557
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Post by vwfence on Jan 25, 2019 21:32:19 GMT -5
the best stuff in Arizona is from over by Mayer around the big quarey there
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Post by fernwood on Jan 26, 2019 2:01:07 GMT -5
Yes, that looks very similar.
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Post by fernwood on Jan 26, 2019 6:42:22 GMT -5
Can you take a picture of where it fractured ? What do you mean by where it fractured? The interior parts (with the black/red) are along the fracture line. They were in the middle of the rock prior.
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