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Post by gaetama50 on Jul 3, 2010 3:14:54 GMT -5
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Post by lauriesrocks on Jul 3, 2010 5:14:17 GMT -5
Looks like corundum. The striations are not at right angles as you would expect in a limonite pseudomrph and it looks to have a slight blue tint, that you would not have in limonite. The crystal form does not look like pyrite either. Shows inter-penetrating crystals, possibly twinned, which could be either one. Do a hardness test.
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Post by romare on Jul 3, 2010 9:45:10 GMT -5
Sure looks like corundum. Do as Laurie says and do a hardness test, that should tell very quickly.
Mark
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Post by 4cornersrocks on Jul 3, 2010 10:10:54 GMT -5
I think it is Sphalerite! ZnS 3.5-4 hardness Look at the edges how they look like bow rosin or pine sap.
I have loads of limonmite replaced pyrite and while this looks close I just don't think it is. Could be though, they are both sulfides and are often found together.
Of course I was just looking at a 1000# plate of Sphalerite in Creede last week so that is probably influencing my guess!
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Post by gaetama50 on Jul 3, 2010 15:02:42 GMT -5
Sorry I dont know why I didn't divulge this information in the initial post, I guess I was just excited. Well, The hardness seems to be about a 5 on the MOHS, and although the indor lighting gives it a slight blue tint, the mineral is almost all dark brown with light brown streaks at the edges and striations. Also the mineral doesn't seem to leave a streak on a white streak plate. Just because of the hardness I dont think its corund. I guess it could be an impure sample though. as for sphalerite I am not familiar with this mineral and will have to look it up. Thanks everyone for chiming in.... you can see why this one has been so difficult  |
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Post by 4cornersrocks on Jul 3, 2010 16:24:57 GMT -5
Sphalerite has a pale brown to colorless streak.
Id'ing rocks is hard!
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