[Rockhounds] Fluororichterite

[Axel Emmermann]

Kreigh
 
> The blue-white spots are blue-white under both LW and SW, and they are
> also phosphorescent blue-white under both (easily a half second).

[Axel] That may be indicative of REE. Spots may come from small crystals of
whateverite-(REE) that are replaced by calcite. The REE are then are
concentrated very locally. 
We have done a survey of the Royal Belgian Institute of Natural History (the
non-public collection of Belgian minerals) and have been looking at some
12.000 specimens that were collected from 1900 until recent times. Some of
the old calcite specimens from the south of Belgium fluoresce a golden
orange with weird spots of lilac (pinkish violet) under LW. The spots turn
blue under SW and have a strong phosphorescence that lasts seconds.
Identical to the Terlingua calcite specimens.
 
> If the reddish orange (under SW) calcite is phosphorescent it is very
> fast. 

[Axel] Yes, Mn + Pb gives really more of a short flash than a clearly
observable PH. I would estimate that it lasts for maybe 1/10 to 3/10 of a
second. 

I was left with the impression of a brief light green
> phosphorescence, but it may be an optical artifact of my eyes/brain.

[Axel]  Green is the complementary color of red. If you 've been staring at
a bright red fluorescence your eyes may retain the afterimage which you
would naturally perceive to be in the opposite color: green.
If the activator is manganese (with lead as a co-activator) you would almost
certainly see the difference. Try it out with a Sterling Hill calcite or a
Peruvian manganocalcite. 
I'm not sure that manganese with another than lead co activator would
display this PH-flash. I just went downstairs for a look-see and behold:

I have two specimens from Terlingua. Both have strong pink fluo under LW and
blue fluo and PH under SW.
Same is true for 3 calcite specimens from Mexico (Nuovo Leon and such).

In LW there is no clear red flash as with the calcite activated by Mn and
Pb.
Ph is to fast or weak to be seen with the lamps on (by pulling the rock into
a dark corner quickly).
By switching off the lamps with eye closed until just after killing them, I
can see a faint greenish glow which could indeed be ph. It was VERY clear in
the Terlingua specimens, which are known to have a high REE content. The
Mexican cleavage rhombs were much dimmer.
One word of caution: blacklight lamps don't die abruptly... the ionized gas
in the tube recombines with electrons over a short time. During that time
the lamps emit UV and the PH of the specimen may in fact be weak
fluorescence. You would need to physically shield the specimen from the lamp
to discern fluorescence from phosphorescence.
Second word of warning: very low levels of light can only stimulate the most
sensitive cells of the retina. These see green so any weak ph would appear
to be green but should really be measured with a spectrometer. Could as well
be blue or yellow....

 
> I would be surprised if specimens taken from different sections of the
> occurrence (either geographically, or in time) didn't have variations
> in trace elements/minerals. 

[Axel] True

I would also expect some variation between
> any two observers of a given specimen.

[Axel] Tell me about it ;-)))))

> Amazing how my list of unknowns keeps getting longer.

[Axel] Eventually it'll get shorter... To about 4 unknowns
1) Who am I?
2) Were am I?
3) Do I need to go to the toilet or did I just go? 
4) Did I get there in time?