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UK yellow needles

Posted by Reiner Mielke  
Reiner Mielke July 14, 2012 05:13PM
This is the EDS results of some yellow acicular crystals that occur as inclusions in calcite. Does anyone have any idea what it might be? Ignore the Ni peak it is an artifact of poor electrical conductivity. Haven't attached a photo as the description says it all.
open | download - Yellow needles Silver C.JPG (27.8 KB)
Uwe Kolitsch July 14, 2012 05:55PM
Is the Ca peak (in part?) due to the calcite?
Reiner Mielke July 14, 2012 05:58PM
Yes the Ca peak is due to Calcite. The locality is the Frontier Mine in Silver Centre, Ontario. This is totally new for that locality. It is from a sample with abundant bismuthinite.
Ronald John Gyllenhammer July 14, 2012 07:58PM
WAG: Something like Tundrite-(Ce)???? but doubtful at Frontier Mine.
Reiner Mielke July 14, 2012 08:21PM
That is what I thought as well. REE minerals are known to occur in the Cobalt camp, I found Kainosite-Y at the Castle Mine in Gowganda and Jambor 1971 in describing the gangue mineralogy of the area mentions the presence of allanite and a bright red "unidentified yttrium silicate" from the Christopher mine.
Reiner Mielke July 14, 2012 08:34PM
Found some more, this time as inclusions in quartz associated with calcite and bismuth.Will post a picture as soon as possible.
Maggie Wilson July 14, 2012 09:45PM

in quartz

FOV 3 mm - my first crack at the new camera/scope set up - it will improve, I promise!
open | download - Frontier MineUK 5.JPG (71 KB)
Reiner Mielke July 14, 2012 11:10PM
The crystals in the photo look brown in real life they are distinctly yellow. Don't know why it turned out that way?
Ralph Bottrill July 14, 2012 11:26PM
Tundrite is possible, though you should see a Na peak.

Reiner Mielke July 14, 2012 11:38PM
Kerry Day did the scan and he said "The lack of Na at this setting doesn’t concern me too much." Not sure what that means exactly, but the sodium peak would normally be at about 1.0 . He also suggested Tundrite.
Ralph Bottrill July 15, 2012 07:24AM
The Na peak is usually relatively weak, especially when you have heavy elements present, but you normally see at least a blip if it's a major component, but instrument settings will affect this.

Amanda Hawkins July 15, 2012 05:24PM
Maggie, judging from your photo they look exactly like Cacoxenite to me, but then I'm no expert on the scientific side.....

Maggie Wilson July 15, 2012 06:29PM
HI Amanda - that was my first guess when I saw the crystals, but the EDS takes us down an entirely different road...
Big V July 15, 2012 08:18PM
could it be a variety of tundrite previously undiscovered? I mean, "K" could easily replace "Na". They're from the same group on the periodic table and they have the same valence as well.
Peter Haas July 16, 2012 08:09AM
"I mean, "K" could easily replace "Na". They're from the same group on the periodic table and they have the same valence as well."

They do not have the same size and therefore, K+ won't replace Na+ that easily.
Reiner Mielke July 17, 2012 11:09PM
Hello Big V,

Interesting point, however analysis of Russain material shows as much as 9 mole% K in the Na position. That could account for the peak. Since K is a much heavier element than Na I would expect it to show up better on EDS.
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