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RE: What is this rock?
I have tried vinegar with no reaction on either the shell or the insides. It does not bubble or fizz like it would on limestone.
I have tried vinegar with no reaction on either the shell or the insides. It does not bubble or fizz like it would on limestone.
Never heard of using vinegar for that test, interesting.
Can you scratch the material with a common nail or flip-knife?
If so, can you do the acid test again on the powder that forms when you scratch the material a little?
Of course, only if there is a part of the sample you do not mind having a scratch on.
I try to scratch the surface with a pocketknife, and it laughs at me. Not even a mark on it. The stuff on the inside is softer, able to be scratched slightly and chipped by the tip of the knife.
The vinegar thing was a trick I learned when I was young as a field identification for limestone. The acid reacts with the limestone and produces carbon dioxide bubbles.
Perhaps more background on the area where this was found will be helpful. In Wyoming there is a rather large area where a specific type of petrified wood occurs called Eden Valley. The reason this wood is unique is that it was submerged in water and encased in algae before it could rot. As a result, the petrifaction process created much opal, basically silica (quartz) that formed under water. I suspect the shell of this specimen is opal, just not a precious type, because the material resembles many other pieces I recovered from the same area.
Yeah, if you cannot scratch it with a pocket knife than silica seems reasonable. But silica ooids are something I have never heard of...
This is another chunk of the opal from Eden Valley, specifically, the Blue Forest. Both this piece and the one in question came from the same area on the same trip. The crystal druzy on the top is calcite.
Another piece of blue opal from the same trip.
This is a piece from the same area but a different trip that I have polished on the ends to show off the swirling of the wood and the opal.
I don’t know if these can help identify my mystery rock, but it should help rule out a few possibilities.
That totally looks like the outside of your mystery rock!
Agreed. What was it that got petrified, though. Seed? Fruit maybe? This has been my mystery...
Thanks for your help :)
Great photos!