Lapidaryforum.net
Let's Rock => Identifications of Materials => Topic started by: Kaljaia on May 03, 2019, 10:14:57 PM
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First time hitting a metallic inclusion. It turned the oil black and smelled like a swamp, so I'm gonna guess pyrite!
In common opal I think, haven't done a hardness test but it cut too soft and smoothly to be a hard agate.
(https://66.media.tumblr.com/6c6e8de941408fe892f21c545951fc9c/tumblr_pqyce4QNkW1rin3o0_1280.jpg)
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Don't forget about marcasite.
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Psilomelane would be my guess. Black oil being the clue.
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Psilomelane would be my guess. Black oil being the clue.
Would manganese have the sulfur smell and rust oxidation tho?
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I can't answer the smell question as my nose has never been worth much. Marcasite and pyrite will oxidize but that is not the same as rust. If you have actual rust then there must be raw iron. That seems a bit unlikely.
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Would manganese have the sulfur smell and rust oxidation tho?
No. Psilomelane isn't a sulfide. Pyrite (streak is dark brown) and marcasite (streak is black) both give off the sulfurous smell.
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I have cut a lot of Nipomo Marcasite agate and it always has that odor and will also turn the water black.
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I have cut a lot of Nipomo Marcasite agate and it always has that odor and will also turn the water black.
Yeah, I figure it's at least FeS2, either Marcasite or Pyrite. The individual crystals look more squared off than the organic forms in Marcasite images, but it's hard to tell. The "Rust" I was referring to is the orange powder and pitting on stone in places. It looks like any metallic surface exposed to air has deteriorated. There was no surface indication of metallic inclusions, only some pitting and orange residue. I'm putting together a little local material "sampler" for ID fun. Do you think "iron pyrite" would be an appropriate label?
Cut another stone tonight with metallic flecks, picked up a few miles away! Apparently it is now the season for metallic inclusions.
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The orange powder sounds like decomposed pyrite not marcasite.
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I would go with the Iron Pyrite label. Lithic is right with the powder and Marcasite (at least the ones I have collected) when they go bad they tend to go gray to whitish powder.
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Ok, I'll go with that! Thanks for help on the ID!
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Limonite is the breakdown product of pyrite and not much fun when you think you have found pyrite cubes but get a closer look and see they are falling apart limonite.