I couldn't find a geology forum or group, so posting here. Has anyone ever seen a rock like this

[Ghost in the Machine]

before? It is mostly red to dark red, but can be seen clearly through when held up to the sun or a light. There is also a good sized piece on it that almost looks like Tiger's Eye. Even stranger, it sounds like glass when you tap it with a metal fork or knife. It was found in the desert around Tombstone, AZ about 20 years ago or so...










I have to leave for a while, so will check in a couple of hours. Any help identifying is greatly appreciated. thanks in advance....

Peace,

Ghost

[SidDithers]

1. Paging MineralMan...nt

Sid

[hunter]

6. Yep.

My guess is obsidian:



https://en.wikipedia.org/wiki/Obsidian

Melted glass, or slag from metal refining comes in all sorts of surprising forms too.

Native Americans traded obsidian over long distances.

[Recursion]

2. Red obsidian?

That could also be a hardened resin of some sort...

[librechik]

3. possibly fire opal

if you are lucky!

[MineralMan]

4. It's obsidian.

Reddish coloration is not uncommon in obsidian. In fact, there's a variety called mahogany obsidian. You have a mixed piece, which shows both the dark brown to black and red color. Very pretty.


BTW, obsidian is a rock, not a mineral. It's of volcanic origin.

[Recursion]

14. ^^^ agreed

This is a colored obsidian

[Xithras]

5. Probably mahogany obsidian

Your pictures are a little fuzzy, but I know a guy who collects meteorite metal in the southwest deserts and he's got a good sized obsidian collection that he's put together over the years. Your photo looks similar to what he has. He makes arrowheads out of them that he sells on Ebay (hint: if you ever see an ebay ad that says "Genuine obsidian arrowheads picked up in the Arizona desert", don't buy them expecting NATIVE AMERICAN arrowheads).

Polished up and carved, mahogany obsidian is quite pretty.

[Maedhros]

7. The conchoidal fracturing evident in your first photo is characteristic of obsidian (volcanic glass)

Here is a reference of known obsidian sources in Arizona:

http://www.sourcecatalog.com/az/s_az.html

Here is a map, which is nice:

http://www.obsidianlab.com/image_maps/map_obsidian_arizona.pdf

There do not seem to be any sources near Tombstone, but I did find USGS Survey Bulletin 2042-B discussing the Bisbee Group of SE Arizona: http://pubs.usgs.gov/bul/2042b/report.pdf

It contained this paragraph, which might be the source of your rock:

Olivine Basalt Dike

A short 2-m thick dike of vesicular olivine basalt containing obsidian xenoliths intrudes a possible basin-range fault in Grand Gulch (pl. 1A). Butler and others (1938) found a similar intrusion in Cenozoic basin fill north of Tombstone.

Hope that helps

[eppur_se_muova]

8. Definitely obsidian. Maybe some fibrous inclusions (rutile or chrysolite) in that "Tiger's eye".

BTW, we do have a Science Group ...

The nearby Chiricahua National Monument features formations left behind by extinct volcanoes ... so it's not too surprising to see volcanic glass in the area.

That's a good-looking specimen, BTW -- most obsidian is much darker, nearly black.

[Rex]

9. Very cool you have a piece of obsidian!

Be careful if it has any sharp edges.

[cwydro]

10. Looks like obsidian to me also.

I have several nice pieces.

[geek tragedy]

11. you could wipe out a white walker with that, good old dragonglass nt

[Egnever]

13. +1

[Ghost in the Machine]

12. Thank you very much for all of the replies. Sorry it took so long to respond but I am still not home

I just checked in on my phone, and it's very hard for me to see, but the concensus seems to be red or mahogany obsidian. The one picture posted by hunter looks very much like what I have.

Again, thanks to each and every one of you who replied with information. Please don't take it personally that I don't respond to each individual reply because, as I said, I am on my phone right now and it's hard for me to see.

Peace,

Ghost

[LWolf]

15. It looks like obsidian to me.

We've got a bunch of it locally.