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Identity Helphaving a tough time with this crystal

15th Nov 2019 05:31 UTCBrian Fussell

Found in Stetttin WI. The crystal is in a rhyolite rock adn am thinking hemetite or possibly thorite both are known in this location. it streaks an orangish color, does not react to UV and unfortunately its to small for me to try and scratch for hardness. appreciate any help.

15th Nov 2019 05:31 UTCBrian Fussell


15th Nov 2019 05:32 UTCBrian Fussell


15th Nov 2019 05:33 UTCBrian Fussell


15th Nov 2019 05:40 UTCcascaillou

Possibly spinel group mineral such as chromite?

While the crystal is too small to be scratched, you might still try and scratch material of known hardness with the crystal (try against copper plate, glass plate, polished quartz).
And actually, the fact that it does leave a streak on porcelain (which may range from 6 to 7.5 Mohs) implies that your mineral is of equal or lower hardness. 

Concerning streak color it is orangish-brown in my eyes.

15th Nov 2019 07:29 UTCFrank K. Mazdab Manager

agree with Alfredo and Thomas.  Also, the yellowish/orange component to the brownish streak could perhaps suggest an additional small jarosite component admixed with the goethite.

15th Nov 2019 06:45 UTCAlfredo Petrov Manager

Looks like a goethite pseudomorph after pyrite.

15th Nov 2019 06:50 UTCThomas Lühr Expert

I wanted to post exactly the same, but you were faster, Alfredo :)

15th Nov 2019 08:04 UTCUwe Kolitsch Manager


15th Nov 2019 12:34 UTCPaul Brandes Manager

Goethite pseudos are known to have come from the Stettin area.

16th Nov 2019 00:35 UTCBrian Fussell

Goethite psuedomorph is something I did not think of...interesting, so why pyrite.. the some what cubic shape?

17th Nov 2019 05:48 UTCD Mike Reinke

I had a similar find years ago, took it to Don Peck, and said the same thing. And yes, to me the somewhat cubic shape is very telltale. Your sample has a more metallic shine than mine did, and that tends to get ones hopes up, I think.  And it is still fun to observe and discern, even if a find is not exotic. If you get any smaller, you will need a microscope, like we talked about in August.

17th Nov 2019 13:14 UTCHarold Moritz Expert

Because replacements tend to have some chemistry in common with the original, in this case iron oxy-hydroxides replacing iron sulfide, and because goethite replacement of pyrite is very common worldwide. I cant really see the crystal form, so cant comment on that, but the streak sure says goethite.

17th Nov 2019 22:39 UTCBrian Fussell

Thank you Harold.

17th Nov 2019 22:46 UTCBrian Fussell

Yes Mike a microscope is on my list of things to get...soon I hope.

It does have a reflective surface, I had a tough time getting the right lighting angles to cut down on the reflections, kinda like when I shoot polished stones.

17th Nov 2019 17:31 UTCDonald B Peck Expert

It says goethite to me, also.  

{Hi Mike, hope the world is treating you well!)
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