What is this rock?

[Whipline]

I got these wierd rocks at a garage sale and was curious what they are. The woman said her dad had them in an aquarium and he was a rockhound so she didnt want to toss them in the field out back. Some one may want them and her father would likely prefer it that way. Unfortunately she didnt know much else. I purchased a group of them. Go easy on me Im new!

 

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[jeff of pa]

looks like a petrified brain lol

petrified brain Coral ?

 

[poorhunter78]

looks like a petrified brain lol

That was my first thought Jeff! Looks like it has some kind of varnish on it..

 

[Whipline]

looks like a petrified brain lol

That was my first thought Jeff! Looks like it has some kind of varnish on it..

Thanks guys! I think you may be on to something. It does seem kinda varnish like on the surface.

 

[High Plains Digger]

In fresh water tanks, coral is a killer. I would only guess that varnish is also. Perhaps a piece of nubby quartz knobs. Maybe take a photo in bright sunlight.

 

[Tuberale]

Petrified alligator head and neck?

 

[ohioaxeman]

Looks like a nasty cancer infested lung!

 

[TheCannonballGuy]

I'm about as sure as I can be that your rock is "cave coral" ...also called "cave popcorn." Waaay back during my high-school and college years, I was a rock-hound ...and a cave explorer. That's why I recognize your rock's distinctive knobby characteristics.

In your photo, you see some grey rock, which is the limestone base-rock that your white-ish cave coral formed on. (On yours, there is also some orange-brown staining from iron in the water the cave-coral formed in.)

Cave-coral / cave-popcorn is one of several types of Speleothem (Greek for cave formation). Your cave coral/popcorn is a variety of the mineral Calcite. Cave-coral forms underwater in pools which are rich in dissolved Calcite. You can see some growing, beneath the cave pool's surface, in the attached photo.

Here's an educational link. http://en.wikipedia.org/wiki/Speleothem

To see other photos, do a websearch for "cave coral" and "cave popcorn."

 

[High Plains Digger]

Cave coral is an interesting guess, but I still am leaning on botroidal quartz. That is the official name of knobby formation. This could have come from a hard rock mining area. I have found pieces similar in the Rockies above Leadville. Just for the record, there aren't too many Rockies higher than Leadville, but some.

A scratch test will tell. Find a piece of calcite. If it scratches the subject, then maybe. But if the same piece doesn't scratch quartz, then one knows for sure. I know, cave coral is a different formation than massive or crystalline calcite, but is is a start. Or, take a piece of the subject and put it in acid. Vinegar is slow, sulphuric acid from an old battery is dangerous, but you decide. Quartz won't be affected by vinegar. The brown stains could be from mineralization in the hard rock.

This is why I said cave coral is an interesting guess based on the photo. All the points were as applicable as mine for quartz.

My second guess would be the alligator neck.

 

[Whipline]

Cave coral is an interesting guess, but I still am leaning on botroidal quartz. That is the official name of knobby formation. This could have come from a hard rock mining area. I have found pieces similar in the Rockies above Leadville. Just for the record, there aren't too many Rockies higher than Leadville, but some.

A scratch test will tell. Find a piece of calcite. If it scratches the subject, then maybe. But if the same piece doesn't scratch quartz, then one knows for sure. I know, cave coral is a different formation than massive or crystalline calcite, but is is a start. Or, take a piece of the subject and put it in acid. Vinegar is slow, sulphuric acid from an old battery is dangerous, but you decide. Quartz won't be affected by vinegar. The brown stains could be from mineralization in the hard rock.

This is why I said cave coral is an interesting guess based on the photo. All the points were as applicable as mine for quartz.


My second guess would be the alligator neck.

A pocket knife wont scratch it but a quarts crystal will? Does this help?

 

[nuggy]

Hi, given it's green color it could be botroidal nephrite jade - which in theory would not scratch with a pocket knife but would with quartz. Botroidal jade in my experience though is often a little softer than good nephrite. Nuggy

 

[Nugget Hunter Smith]

From a prospectors viewpoint, that is a leaverite. As in, leaver right where you found it, as there is no gold in it.

 

[heepiepow]

yuck it does look like brain or lung in caramel sauce.

Heh. Yeah, I was thinking BBQ sauce and it's making me hungry.

Not sure if it's true botroidal, looks more like normal weathering or the deposition process (cave popcorn! Wow, neat stuff!)

 

[bradyboy]

looks like my liver
Brady

 

[Ralphw]

from what I understand cured epoxy is fish safe..... at least thats what the Koi people say and I hope they are right cause I'm sealing my cement waterfalls with it....


odd rock for sure

 

[High Plains Digger]

Your scratch test is not definative yet. It is good that a knife blade doesn't scratch it, but quartz on calcite will leave a scratch and quartz on quartz will also. So we still don't know much. Do you have some acid to drop on it? Quartz will not react to most acids while I believe calcite will. Jade can be scratched with quartz, also. So a couple of more tests are in order! How about trying to scratch a piece of quartz with a piece of the aligator throat/brain/liver. If you can take a piece of the white off without mucking up the rest of the sample.

I don't know about cured epoxy, may be ok, and I don't know about varnish, but it scares me for fish, but I do know I killed some fish after putting in shells and coral that weren't coated. Calcite, in another form. Then the aquarium guy told me not to do that.

Cave coral is still interesting as a possibility. 50/50 with quartz, I suppose, in my book.

 

[Whipline]

Your scratch test is not definative yet. It is good that a knife blade doesn't scratch it, but quartz on calcite will leave a scratch and quartz on quartz will also. So we still don't know much. Do you have some acid to drop on it? Quartz will not react to most acids while I believe calcite will. Jade can be scratched with quartz, also. So a couple of more tests are in order! How about trying to scratch a piece of quartz with a piece of the aligator throat/brain/liver. If you can take a piece of the white off without mucking up the rest of the sample.

I don't know about cured epoxy, may be ok, and I don't know about varnish, but it scares me for fish, but I do know I killed some fish after putting in shells and coral that weren't coated. Calcite, in another form. Then the aquarium guy told me not to do that.

Cave coral is still interesting as a possibility. 50/50 with quartz, I suppose, in my book.

Apparently these stones are a botryoidal nephrite jade. Rare but supposedly found by this guy up in the Sultan Basin. Jade. What do ya know...LOL

 

[High Plains Digger]

Jade is way cool. Perhaps that is why it looks like it has a coat of varnish. Know anyone that has the tools to make some cabs? I would love to see some slices of your aligator throat. Good thing you got that figured out, but how? The thing about jade--it is a "tough" rock, but relatively soft for the scratch test. I personally love white jade--also called "mutton fat", which this rock apparently looks like, but I'll bet there is some mixed color pieces to come out of it.

Just looked back--Nuggy said jade, bigtime. Whohooo! Tell us more about jade, nuggy.

 

[nuggy]

Just got back to this thread and looks like maybe I was right for once lol. Well jade carving is mostly what I do for a living but I was unsure just identifying from a photo.

Plenty of books and also online stuff about jade if you want to know more, nephrite jade and jadeite are both called jade but are two different minerals. Jadite was reasonably common in South America - Aztecs etc carved it. North America seems to have mainly nephrite - well know deposits in California, Alaska, Wyoming and British Columbia. Nuggy

 

[Tuberale]

If interested, I've got a piece of black jade from a Washington jade claim. Stayed overnight with a couple from Bellingham while I talked about truffles around 1993. The guy was a retired petrochemical geologist for Shell Oil Co., and had a fantastic collection of preserved fish-in-mudstone skeletons, all identified to genus and species. I saw this black piece on one of his display shelves, and asked if it was jade. He said it was and gave it to me. Also said most people have never heard of black jade, but he had a mining claim in WA with black, green, and several other colored jade present. Interesting piece.

I understand there are boulders of jade off the northern CA coast as well.