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Let's Rock => Identifications of Materials => Topic started by: Johnny.Pilgrim on June 01, 2022, 04:40:07 PM
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Hello!
I came across this little gem the other day. 110 lbs.
any thoughts on the rock and mineral composition?
Fresh water agate and geode formation?
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Very hard to give an exact answer without more hints like where it is from, possible hardness, a streak color, does it react with weak acids like vinegar. My first guess 99% is that it is a Calcite/Onyx. Can you scratch the crystals with the edge of a knife? Not sure your experience if you know how to test hardness and streak etc. The knife is a simple test in that a knife blade will not scratch agate since most knives are a 5 to 5.5 and agate is a 6 to 6.5. Calcite however is down around 3 to 3.5. If vinegar fizzes on the stone or crystals then they are likely calcite based, items such as limestone also fizz as the acids react with the calcium. The other clue is the degraded nature of the surface of your material indicating a softer material like calcite. Nature doesn't erode agate easily but what you have has been tortured by the elements and that screams soft material likely easily dissolved. Was it found near a hydro thermal area?
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Hello!
I came across this little gem the other day. 110 lbs.
any thoughts on the rock and mineral composition?
Fresh water agate and geode formation?
Oh what a big one! Just wandering what your gonna do with it? I have very little experience in gemology. I find it very interesting though...
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It looks like a sediment , possibly tufa or limestone that was metamorphosed.
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Hi Y’all, thanks for the response and ideas. I did try the vinegar and file. For hardness some areas I could not scuff while others I was able to leave an abrasion. The sandy beige portions seem to be a condensed or hardened sand or sediment. While other portions have bands of different colors and are much harder. The vinegar didn’t seem to have an effect where ever I poured it. While it does resemble tufa and limestone I’m curious what the crystal formation is? The colors range from brown, rust, to red. Thanks again for the responses.