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I have found several grey rocks like this one on a beach along the ocean and I don’t know what they are. This is the only black one I’ve ever seen. Anyone know what it is?
enter image description here

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closed as off-topic by user12525, arkaia, Fred, trond hansen, Friddy Jul 11 at 17:21

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Please review our rock identification guidelines to provide the missing information so that your question is both answerable and useful to new users." – Community, arkaia, Fred, trond hansen
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ density and hardness are important. It could be just weathered asphalt. $\endgroup$ – John Jul 22 '18 at 6:20
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    $\begingroup$ Sylvie, where do you found it? wich ocean? please provide precise location if possible. That help us to give you a better answer. Also provide a scale, we don't know if that piece is 2cm or 50cm. Anyhow it looks to me like a volcanic piroclast. $\endgroup$ – user12525 Jul 22 '18 at 6:57
  • $\begingroup$ If so, as said, density would be helpful. Volcanic piroclasts use to be very lightweight because they have a lot of holes. Sometimes are extremely ligthweigth in relation with his volume. $\endgroup$ – user12525 Jul 22 '18 at 9:09
  • $\begingroup$ Does it float in water? $\endgroup$ – Spencer Jul 25 '18 at 1:51
  • $\begingroup$ This question closed, over a year old without additional information to make the question more accurately answered. $\endgroup$ – Friddy Jul 11 at 17:20
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It looks a lot like basalt. Basalt comes in several shades of grey and black.

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  • $\begingroup$ please expand your answer,one liners are not very helpful when giving answers on theis site. $\endgroup$ – trond hansen Jul 11 at 14:17

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