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Improving Mindat.orgCobaltite on safflorite?

13th Jan 2016 18:40 UTCReiner Mielke Expert

http://www.mindat.org/photo-726449.html they look like skutterudite crystals to me. I have analyzed dozens of such crystals and they are always skutterudite. Cobaltite does not occur like that, it is almost always as anhedral inclusions in other arsenides. Of course this could be the exception but that would need to be proven with EDS.

13th Jan 2016 18:58 UTCRob Woodside 🌟 Manager

The only good cobaltite xls from Cobalt that I know about are from the Columbus mine in a green matrix. All this material analyses as Reiner says.


Reiner, do you want him to x-ray the safflorite?;-)

13th Jan 2016 19:16 UTCReiner Mielke Expert

Since they are crystals EDS will do the job just fine. Otherwise you would need to do XRD to distinguish from alloclasite.

14th Jan 2016 00:06 UTCRob Woodside 🌟 Manager

Check out the "cobaltite". Use the mouse wheel to magnify. The wedge shaped and striated ones might be lollingite? Skutterudite can be misshapen, but I've never noticed striations.The piece also appears to have chalcopyrite.

14th Jan 2016 00:53 UTCReiner Mielke Expert

Yes you are right, never bothered doing that but they are definitely striated and some appear elongated and some pointed. Those are arsenopyrite, very common on safflorite. Lollingite does not form crystals like that, they look like safforite crystals which suggests that maybe the safflorite is lollingite. However lollingite is rare in Cobalt safflorite is far more common. One way to tell safflorite from lollingite is lollingite weathers brown whereas safflorite turns pink.The brownish stuff is probably nickeline not chalcopyrite which would be tarnished blue if it were ( because of the silver nearby). The presence of nickeline also works against lollingite, have never seen lollingite together with nickeline. There appear to be a couple squarish crystals that may be skutterudite, not uncommon to find arsenopyrite and skutterudite together.

14th Jan 2016 02:16 UTCRob Woodside 🌟 Manager

Thanks Reiner. I was going to call the striated xls arseno as that's what they look like but the arsenides made me think lollingite. Elsewhere lollingite is often confused with arseno, but at Cobalt I've never seen lollingite xls that looked like arseno. I thought this might be a first.


The tiny "yellow" bits don't seem brown enough to be niccolite on my monitor. How long does it take after etching for the chalco to tarnish blue? This maybe specious but chalco makes sense with arseno as the Fe is common to both.


There are not a lot if any star shaped twins in the "safflorite".


The squarish xls are certainly skutterudite.

14th Jan 2016 14:51 UTCReiner Mielke Expert

Could be chalcopyrite, a close examination is required we sure are not going to be able to determine what it is from the photo. All I can say is that I have never seen chalcopyrite on safflorite but lots of nickeline.

26th Jan 2016 23:48 UTCTony Peterson Expert

07975570016033490266635.jpg
Hi Guys - I had difficulty finding a small piece to knock off for analysis that didn't mar the specimen. But I found another area with those embedded crystals and these are very silvery; I agree with Reiner that most if not all are skutterudite. See attached photo, FOV about 6 mm.



So I will alter the photo to have sk'ite instead of cobaltite; I will check the specimen under a scope to see if some arseno can be seen. Will that suffice?


Oh and, what is the white mineral in the image?


Tony

26th Jan 2016 23:51 UTCReiner Mielke Expert

The white is probably quartz left over after the specimen was etched out with acid. Only the crystals without the striations are skutterudite the others are arsenopyrite.

27th Jan 2016 02:32 UTCTony Peterson Expert

OK!!
 
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