kurts
Senior Member
Posts: 82
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Post by kurts on Apr 28, 2009 2:07:54 GMT -5
I thought mineral buffs might enjoy seeing a rock I found today. This caught my eye from a distance, due to high reflectivity of the crystal faces. It's a rather hard material, where a light draw across my Swiss army knife regrettably left a fine, deep grove. It also scratches quartz very easily. This is mixed with calcite and a few other minerals. (Photo is composite of several shots)  |
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Post by jwnagy on Apr 28, 2009 11:18:00 GMT -5
I'm confused.... ;D
If it scratches quartz, that means it's harder than quartz (mohs 7), yet you said a knife (mohs 6) scratches this unknown material?
??
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Post by Mineral Salvage on Apr 28, 2009 12:33:05 GMT -5
It looks like a type of quartz to me. Remember... quartz will scratch quartz, not as evident as softer material, but minerals of the same hardness WILL scratch eachother, but you may have to use a lens to see the minute sratch.
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kurts
Senior Member
Posts: 82
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Post by kurts on Apr 28, 2009 12:58:14 GMT -5
"... a light draw across my Swiss army knife regrettably left a fine, deep grove" The knife doesn't mark the mineral. I drew a crystal edge across my knife blade and the result was a deep score-- poor choice of words I guess. ;D It's like a burin on steel--I regret testing that way LOL. I take photos of everything--here is the very clean, deep mark on the steel blade (microphotograph)  I thought the rock made for an interesting photo. I should note this mineral has a distinctly different luster than quartz and the crystals don't terminate like quartz found at this California site. I have an idea what this is, as I've seen the crystaline shape before, particularly on the unfinished girdles of cut gems. I need to go back to this site, because I once saw some brilliant blue crystals...which in retrospect might be the same thing. The area is a site of limestone/marble/serpentine with intrusive and fault-based metamorphism. Thanks for dropping by!  |
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Post by amythestguy on Apr 28, 2009 14:35:58 GMT -5
Hey I love what you did with the pictures up above..very cool, if you get a chance do some more..it would make a great picture painting
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kurts
Senior Member
Posts: 82
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Post by kurts on Apr 28, 2009 14:40:32 GMT -5
Thanks! These are screen grabs from a QX5 microscope. The crystals are quite small...but I'm going back to find larger ones. |
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kurts
Senior Member
Posts: 82
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Post by kurts on Apr 29, 2009 23:41:29 GMT -5
Well, as an update--I covered miles of terrain today without finding another definite sample of corundum. The sample above was identified as corundum over on Mindat, as I suspected...the crystaline structure is very similar to "naturals" I see on cut sapphires and rubies.
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