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Another help me identify thread....


sirk76

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Hello everyone,

I'm new here and know exactly nothing about rocks and minerals. I found this rock so long ago I can barely remember finding it. I have no idea what it is or where to begin.

Here goes, the only thing I know about it is that it weights about 22lbs and looks like a large chunk of glass.

post-25994-0-35569300-1325193022_thumb.j

post-25994-0-47188700-1325193036_thumb.j

post-25994-0-83548900-1325193050_thumb.j

Thanks,

Kris

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Steve,

This rock was found around Greensboro, NC. It has become kind of a family argument about its exact origins but I distinctly remember digging it up. I must admit that I was disappointed to hear Bobby say it looks like glass to him too.

Kris

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A hardness test will verify. It is vitrified silicon dioxide (glass) and I believe it is man made. If it is a natural mineral it will be softer than glass so you can probably make that determination with common materials of known hardness.

I don't want to discourage you but that is my call. I certainly could be wrong. Especially if the stuff was soapy soft.

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Definitely not soapy soft. I read a little about hardness testing and tried a few things to test it. With the materials I have, a penny and a utility knife, I was not able to scratch it at all. So from my limited knowledge the hardness is definitely above an H6 on the Mohs Scale.

Is that conclusion correct? What does it tell us?

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I know that you can buy this type of glass at mineral shows all over the country. Or at least you used to be able to. I have a few pieces of dark purple glass that can almost pass for obsidian unless you hold them up to the sunlight and check the color.

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The crude hardness test that you performed just needs to be backed up by learning about the physical properties of silica minerals. Not all silica minerals are softer than glass but most that look anything similar to yours are. So it was a quick and dirty way of making an off the cuff mineral identification.

Pick up any field guide to rocks and in the first few pages it willl tell you all about the steps to identifying a mineral. Color, fracture, luster, hardness, streak, density, etc.etc. Then, the guide will be layed out in such a way that as you go through the steps of identification you can eliminate possibilities. Once you have boiled it down to two or three possibilities it generally becomes clear. It will teach you how to crudely identify a mineral for yourself and then you can use that technique in the future.

I bet it is glass. From the photo and the info given that is my call. If I were you I would use that find to teach yourself the basics of identification. In that respect the specimen is priceless.

Bobby

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