Coarse-grained...

Coarse-grained...

In WS part of "Staroscinskie Skaly" I observed coarse-grained granite covered probably by black mineral called goethite.
Romuald Kosina
on Jul 25, 2007 1:12 pm
Image ID: 316159

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Dan Dalton

Dan Dalton - Jul 25, 2007 1:24 pm - Hasn't voted

Huh...

you stumped me, I have never heard of this mineral before. I am going to have to go and do some research!

Dan

Romuald Kosina

Romuald Kosina - Jul 25, 2007 1:34 pm - Hasn't voted

Re: Huh...

MMDan, do not affraid so much!!!! :-))))))
I wrote "probably". This granite has a little inside a powder of limonite with good green fluorescence. There is possibility to create a layer of psylomelan, however, I also must check it with some help of my friends, mineralogists. Now I know that this black layer is of mineral origin, not from fire or pollution.
Nice to hear you again!!!!!!
Cheers!!!!!
Romek

Romuald Kosina

Romuald Kosina - Jul 26, 2007 2:00 pm - Hasn't voted

Re: Huh...

Hi, MMDan!!!
I looked at this mineral under microscope, also on pieces of rocks from another mountain in Rudawy (Wielka Kopa) and, provisionally, I can change this determination, rather it is not psylomelan, there are visible good transmissions between hematite and goethite like pseudomorphosis.
Of course it will be more studied, maybe by X-rays analysis.
Cheers !!!
Romek

Dan Dalton

Dan Dalton - Jul 26, 2007 2:32 pm - Hasn't voted

Re: Huh...

Right on! This is turning to be a quite interesting mineral identification. I have always had a hared time in thin section or under the scope identifying less common minerals. If you get the chance, x-ray difraction will be able to tell exactly the chemical make-up and what mineral it is. Keep me posted!

Dan

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