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Post by Drakien on Jul 6, 2013 1:56:00 GMT -5
I have here a Dark Gray Metallic rock with a blueish/purple tint to it. It streaks gray-dark gray. This is fairly brittle around the edges, but in a whole is quite strong. It has a fiber-like structure. Hosts pyrite. Non-magnetic, not even slightly(tested with a fairly good sized neodymium magnet). The piece I am using for photographs is approximately 2" in length. So what you see here is the blueish/purple tint. Here we are looking at under a microscope. Still has that blueish/purple tint. Pyrite(brassy yellow) and what appears to be a moss or mold(bright yellow)? Pyrites under the microscope. Yellow growth? under the microscope. (Scratches off quite easily) I am not to concerned about the growth or the pyrite, I am just curious on the host rock. In case locality is important, I am not exactly sure where the location is, but it is in Southern Utah.
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Post by fishermenrock on Jul 9, 2013 10:43:06 GMT -5
i have found a piece that looked like this at my work, but they were mine tailings from the local iron mines
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what
Junior Member
Posts: 3
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Post by what on Sept 4, 2013 12:37:18 GMT -5
Check hardness and that will give you a good idea of what groups to look at.
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what
Junior Member
Posts: 3
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Post by what on Sept 4, 2013 12:41:08 GMT -5
Also, how can I be of help when I am not allowed to view rock pictures and get a message that this forum has exceeded it's space limits bla bla bla. What sort of place is this?
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Post by dstacks on Nov 4, 2013 21:07:57 GMT -5
This is molybdenite.
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Post by jollyrockhound on Nov 5, 2013 22:22:16 GMT -5
would say so or galena
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Post by dstacks on Nov 6, 2013 23:15:55 GMT -5
A specific gravity test would easily determine between the two. There are also obvious differences in cleavage, hardness and tenacity (flexibility) between molybdenite and galena, but pyrite is a common association with both. I would hope that something as heavy as lead would be distinguishable. The oxidation of molybdenite sometimes produces molybdite, which is often a yellow color like the "moss" or "mold" mentioned. However, the presence of pyrite often inhibits oxidation of molybdenite and the mineral is very soft and brittle, not "quite strong" as Drakien attests, so I should probably not be so definite in my identification. This free site often helps me with identification - www.mindat.org/min-2746.html
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