Thread: Need help identifying a "rock"

Hello. I found this object in central New Jersey approximately 20 miles from the coast. I don't know much about geology/petrology so I've come to you for assistance. It was found in a remote location in the forest so I would expect it to be a natural formation but I could be wrong. It is magnetic. Google searches lead me to believe it's a "coal clinker". Can anyone identify it? Thank you in advance

I've referred to my copy of Dorling Kindersley Handbook for Rocks And Minerals, and the following two specimens appear to bear some similarities to your photograph. Until someone else comes in to identify what your specimen really is, perhaps these might be what you're looking at.

IMG_0397.jpgIMG_0398.jpg

* I think the "rounded cavaties" shown in the Vesicular Basalt entry is highly similar to what you have. I've also found a similar image with a specimen identified as Scoria.

Scoria.jpg

Thank you for your response scoobydoo1. You're right, they are very similar. One detail I forgot to add is the surface is smooth and looks almost glazed as opposed to a gritty texture like sandstone. Unfortunately the picture was taken with my phone so the color is also slightly off. It's a bit darker than what the picture shows. Can Vesicular Basalt have those characteristics? If so, you are probably correct. Please excuse my lack of knowledge!

It looks like this pumice stone I found on a website selling beauty products.


Does it float if you put it in water?

Originally Posted by mmjwski

It's a bit darker than what the picture shows. Can Vesicular Basalt have those characteristics? If so, you are probably correct. Please excuse my lack of knowledge!

I think I ought to let the more experienced and qualified forum members answer that. To be honest, I do not even qualify as an amateur in the subject of Geology. I'm just a person with an above average curiosity on rocks and minerals and find the processes that produces them fascinating. Plus the handbook does have a lot of colorful and pretty pictures.

Just tested. It sank straight to the bottom. I find it very heavy for its size and the amount of cavities it has. I'm tempted to crack it open but it's been in my possession since I was a child and as silly as it sounds it has some sentimental value to me. Although that may be the easiest way to identify it

It looks like an iron meteorite, only a small one. It being magnetic brings to doubt that it is pumice. And it being heavy for its size and sinking.

Originally Posted by scoobydoo1

I think I ought to let the more experienced and qualified forum members answer that. To be honest, I do not even qualify as an amateur in the subject of Geology. I'm just a person with an above average curiosity on rocks and minerals and find the processes that produces them fascinating. Plus the handbook does have a lot of colorful and pretty pictures.

Either way I really appreciate the help. I'm clueless when it comes to stuff like this

Originally Posted by mmjwski

Just tested. It sank straight to the bottom. I find it very heavy for its size and the amount of cavities it has. I'm tempted to crack it open but it's been in my possession since I was a child and as silly as it sounds it has some sentimental value to me. Although that may be the easiest way to identify it

If it sank right away then it is probably scoria as scoobydoo suggested. pumice floats for a bit before sinking.

I'm not an expert either. Not even a hobbyist. Is it magnetic? Pyoko mentioned it but I couldn't find were you had said anything about it being magnetic.

It shouldn't be too hard to get it identified without destroying it. we had to identify rocks in earth science in 7th grade. We used various chemicals and litmus paper to identify some rocks. You can probably call your local highschool and speak to the earth science teacher there. If they can't help you, they likely can tell you where to get help.

An iron meteorite would conduct electricity whereas a lot of terrestrial iron rocks would not. You could try measuring the resistance with a multimeter.

Originally Posted by pyoko

It looks like an iron meteorite, only a small one. It being magnetic brings to doubt that it is pumice. And it being heavy for its size and sinking

After being submerged (this is the first time it's been cleaned other than dusting it off) the color and texture look very similar to your picture. The only difference I can see would be the depth of the cavities

Originally Posted by seagypsy

If it sank right away then it is probably scoria as scoobydoo suggested. pumice floats for a bit before sinking.

I'm not an expert either. Not even a hobbyist. Is it magnetic? Pyoko mentioned it but I couldn't find were you had said anything about it being magnetic.

It shouldn't be too hard to get it identified without destroying it. we had to identify rocks in earth science in 7th grade. We used various chemicals and litmus paper to identify some rocks. You can probably call your local highschool and speak to the earth science teacher there. If they can't help you, they likely can tell you where to get help.

It is slightly magnetic. Thank you for the suggestion. I just might do that in the morning

after re-reading the op a 6th time i finally see where you DID say it was magnetic. I do think my eyes hate me. how i missed that 5 times i do not know. Had i noticed it, i would not have suggested pumice. oh well, no harm done.(except to my ego)

Originally Posted by pyoko

An iron meteorite would conduct electricity whereas a lot of terrestrial iron rocks would not. You could try measuring the resistance with a multimeter.

That's very interesting. If my brother hadn't borrowed my multimeter for the weekend I'd be able to test that now. Looks like I'll have to wait on that. Great piece of information

Originally Posted by seagypsy

after re-reading the op a 6th time i finally see where you DID say it was magnetic. I do think my eyes hate me. how i missed that 5 times i do not know. Had i noticed it, i would not have suggested pumice. oh well, no harm done.(except to my ego)

No worries
You've all given me some great leads and I'm sure it will be identified soon enough. All thanks to the people posting in this thread

Its not a meteorite, the pitting on the surface is air pockets. I would second the vesicular basalt suggestion. The Basalts in the New Jersey/New York region are metal rich and slight magnetism is to be expected.

Originally Posted by mmjwski

You've all given me some great leads

Yes, just hook them up to the rock and measure the resistance.

As am amature I would suggest that there are a couple things you could do to get precise data about your rock. One would be get an accurate density using the archmedian method. Test it for hardness with scratch tests. Does it react to acid or basic solutions? you have already tested for magnetic qualities. All that being said it looks a lot like a bit of cooled and aged lava. I recently spent a month in Hawaii and note that the lava flows can be dated by their color, it is coal black when fresh, but becomes browner as it weathers, eventualy degrading to a red soil.