Can anyone identify this rock?

Posted: Tue Jun 14, 2011 8:43 pm

Though it looks brown, it is black on the outside and inside..I was able to knock a chip off it. Put it on my grinding wheel..grinds smooth like metal(small piece)..turned gray..non-magnetic..any ideas?

[img]

[/img]

Posted: Tue Jun 14, 2011 11:23 pm

possibly some kind of sedimentary rock maybe?

Dredger Joined: 22 May 2010 Posts: 605

Lots of possibilities.

Streak test?
Hardness?
Specific gravity?

Help us help you.

Sam

Posted: Wed Jun 15, 2011 5:02 am

try a streak test like sam said

just use a small square ceramic tile and scrape a chip of the rock or the rock itself on the tile.(just scrape it straight from top to bottum and post a good close up pic of it)

Posted: Wed Jun 15, 2011 2:51 pm

Thanks guys..I could not get a good pic of streak test..left a gray streak..rock is gray inside..looks black when wet..can scratch it with a pocketknife.. lighter than quartz of the same size..sorry, I don't know anything about checking a rock..

This is a 10X pic of the chip..it has red,yellow,green and silver colors in it..thanks...gene

Posted: Wed Jun 15, 2011 3:59 pm

My guess is slag. (Skim off from metal forming.)

But, I'm no Geologist. (I was a manufacturing Engineer.)

AND I stayed at a Holiday Inn Express last night! Laughing

Take it to a university, they could tell you in a minute.

Dredger Joined: 22 May 2010 Posts: 605

Likely an oxide of manganese...maybe Braunite, maybe not.

Manganese has a hardness of 6, which is harder than a pocket knife, unless the knife is hardened steel. So if regular steel it isn't manganese, nor braunite, even though it definitely has manganese stains on the outside.

Sam

Posted: Wed Jun 15, 2011 5:23 pm

My guess is either andesite or basalt with some kind of olivine and pyroxene crystals accounting for the colors.

Posted: Wed Jun 15, 2011 10:12 pm

Astrobouncer wrote:

My guess is either andesite or basalt with some kind of olivine and pyroxene crystals accounting for the colors.

I was thinking basalt too..

Posted: Wed Jun 15, 2011 10:51 pm

Thanks Sam, Astro, C49er and madhatt3r...took the names and been chasing down pics..got it narrowed down to basalt or gabbro..everything points to basalt...What is volcanic rock doing in middle Ga. ?...csu at pompano geology has a ignieous rock ID program online. I don't think ya'll need it but I used it to see what it would say...Basalt...Thanks again...gene

Posted: Wed Jun 15, 2011 11:01 pm

goldwind wrote:

Thanks Sam, Astro, C49er and madhatt3r...took the names and been chasing down pics..got it narrowed down to basalt or gabbro..everything points to basalt...What is volcanic rock doing in middle Ga. ?...csu at pompano geology has a ignieous rock ID program online. I don't think ya'll need it but I used it to see what it would say...Basalt...Thanks again...gene

volcanic rock which made the earths crust and thermal vents too

Posted: Thu Jun 16, 2011 10:37 pm

madhatt3r...that makes sense to me..I was thinking thousands of yrs ago...should have been Millions..thanks

Posted: Thu Jun 16, 2011 11:02 pm

yeah...you can really get technical about it but thats basically it.