Really weird obsidian??? And other???

[Geodad]

Hi Everyone,

My daughter and I were out picking through rocks again and she found another really cool looking one which I told her was Micah but to be honest I don't know much about rocks so I am looking for help with identifying it.

Also, years ago while working on a construction site I was spreading out some loam with a skid steer when I noticed a large chunk of black glass. I took it home and later realized it was most likely obsidian but I'm not sure because it was found in western Massachusetts and from what I've read its pretty rare around here. However, I was close to the Berkshire mountains so maybe it's possible. Also, the material was trucked in so who knows where the loam came from.

It has a really strange nipple indent in the cup and on the other side is what I'm assuming is an air bubble but I would really appreciate some knowledge about this rock/glass whatever it may be. I'm planning on breaking it up and putting it through my tumbler with some ceramic media to make sure it doesn't break. What do you guys think?

 

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[Steve1236]

Hi Geodad, what your daughter found is most likely Chalcopyrite, the black could be manganese, I think you have slag and not obsidian but I could be wrong, sorry I can't be more of help.
Steve.

 

[Geodad]

thanks, I will look into that and see if the description matches what I have

 

[ArfieBoy]

The second is definitely obsidian. There is a lot of it here in the Pacific Northwest if you know where to look. I don't know about the first one.

 

[Noah_D]

Fellow TNetter's,
On a different thread Cannonballguy pointed out that there is a small mound and corresponding depression on the 'obsidian.' Just something to think about. Look at the other thread... http://www.treasurenet.com/forums/what/632348-obsidian-other-rock.html#post6489122

 

[Geodad]

the only problem I have with the glass bottle theory is that the thickness of the "glass" is not at all uniform like one would expect from a glass bottle and the mound and dimple just don't line up like they should

 

[Noah_D]

I don't think TheCannonBallGuy is on the rocks and minerals forum but I don't know too much about Black Glass, he is reputable and usually knows his stuff. I just wanted everyone on this forum to know what his opinion was before a 'diagnosis.'

 

[Moesia]

Your pictures lack focus, but from what I can tell first set of pictures pyrite, pyrrhotite, pentlandite, chalcopyrite are all a possibility. You need to do a streak test to have a more accurate guess. Second set of pictures is glass/slag.

 

[DDancer]

Picture 6 pretty much defines your glass as a broken bottle bottom as Noah and Cannonball pointed out. The depression and the side of the bottom of the bottle are definite. Those bottles were pretty heavy in the day. A cool find btw. I'm in general agreement about the mineral in the first 4 pictures. As Moesia says, a streak test would help. Better focus on the material as well because its difficult to tell if it might be a Mica as you presumed earlier, but it does look good for a possible pyrite~ just cant tell with the pictures.

 

[Geodad]

So I did a scratch test and I was able to scape some material off very easily with a knife. (first material) I believe it fits the description of chalcopyrite the best. As for pics with better clarity; that's the best I can do with my iPhone. I wish I had a better camera but unfortunately that's the best I can do. I'm going to upload some pics of the black glass/obsidian. I think you guys will change your opinion after this new angle as it allows you to see that the bottom dimple is not even close to lining up with the other sides hump.





This last picture; I am holding the pen right where the concave dimple is on the other side. See how the curve and edges don't line up?

Also not sure why the pics loaded in horizontally sorry about that.