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What are those two stones?

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Hi guys, does anyone knows about these two stones are picked up on the beach? the last one is very black and when I scratch it against a white fabric, it leaves a few black mark. alt text alt text

asked Nov 6, 2014 by freesix (160 points)

3 Answers

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1st one looks like quartz veins in host rock. Second one is likely waterworn coal or graphite if if it smudges as you describe.

answered Nov 9, 2014 by hershel (47,460 points)
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They are beach worn, abraded by the sands. Where did you find them? That will give us some idea of the rocks and minerals in that area.. Is the black one magnetic? Can you scratch them with your fingernail, a coin or a knife or perhaps another rock of a known hardness such as quartz. Answers to these questions will help with identifying your rocks.

answered Nov 9, 2014 by Weasel (39,680 points)
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Thanks for replying to me.

I stay in South Africa, in Cape-Town precisely. So I found them on the beach of Cape Town.

No, the black one's not Magnetic, but when I try to scratch it against a white fabric, it leaves a very few black mark.

I tried to scratch the black one with a knife but I found nothing, I mean it only leaves black scratch mark; and it's tough if you try to scratch it but it's not really heavy.

answered Nov 11, 2014 by freesix (160 points)

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