How to identify a metal ?

Hi ! Into a terrain near a very old volcano and a river, my brother found fragments of obsidian of various sizes and colors. Some of them are "glued" to metallic stones, and some others contain marbles of metals ... He also found a heavy metallic rocks (encrusted with obsidian) who reacts with magnet, and an other light one (without obsidian) who does not react with magnet. Do you know a mean to identify those metals ? (I Googled but found nothing very useful so far) Or do you have a clue of what it could be ? #1 is a metallic rock encrusted with obsidian. It must be iron because it's heavy, the rust is red, and it reacts to magnet. #2 and #3 is obsidian with marble of metal who reacts to magnet. #4 is an unknown (metallic ?) rock. It is light (150 grams for 200 cm3 - 0.33 pounds for 12 cubic inches), of the color of silicon (or the graphite of paper pen !), does not react to magnet but is (electric) conductor with resistance near 0 ohm.

sort by: active | newest | oldest
1-10 of 42Next »
royalestel10 years ago
This may just be ignorant, but could you use one of the DIY spectroscopes on the site for identifying elements in the rocks?
. hmmmm I tried searching for spectroscope/spectrescope/spectrascope/spectriscope and didn't find anything.
Try spectrometer
. Thanks. I found this (putting spectra in quotes in the title threw me off, it was in the 'scope hits), but it's only for visible light. Not sure that will work in this case (though it might give some valuable hints).
Oh, you know I think I was confusing spectrometer with spectroscope.
chooseausername (author)  royalestel10 years ago
I'm not sure, but I think spectroscopy only apply to gas ... :o/ I remember few month ago, I've read an article where it explained spectroscopy. If I recall correctly, there are two methods : 1) you heat the gas sample and you analyze the light emitted by the sample ( you'll get a "positive" spectrum : emission spectrum ). 2) you light the gas sample with a white light and you analyze the light filtered by the sample ( you'll get a "negative" spectrum : absorption spectrum ).
. Since you weren't sure, I did a Q&D search on spectroscopy and found "The branch of physics concerned with the production, measurement, and interpretation of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances." - Cotton, Inc. (my emphasis)
chooseausername (author)  NachoMahma10 years ago
Though "various" does not mean all ... :o/ Because, for gas and transparent liquids or solids, I imagine it's possible to get the absorption spectrum by using this gas or this transparent liquid or liquid as a filter. But for opaque substances, the only mean (with spectroscopy in the domain of the visible light) would be to analyze the "reflected" light ... but will it work correctly with tiny and "non flat" samples ? :o/ As soon as I'll have made a spectrophotometer or a monochromator, I will try anyway :o)
. That was just a representative sample. I looked at 5-6 defs and none specified the state of the material. . I didn't spend much time reading, but from what I gathered there are three types of spectrography: stimulated emission (bombard it with energy, eg, x-rays), absorption (pass a light (not necessarily visible) of known spectra (spectrum?) through the material), and reflective (not sure, but I'll bet it means what it says; might involve polarization). . Now that I think about it, when I was in school, we had a device that was shaped like a small telescope with a flare on one end. If you pointed the flared end toward a light and looked in the other end, you would see the spectrum. No power was required. Maybe you could stick something like that on the front of a camera and use the images to to do some analysis. . > monochromator . I learned a new word!
chooseausername (author)  chooseausername10 years ago
Though, if I can make a spectrometer, I will, for sure, try it on solids samples =o)
1-10 of 42Next »