Hyalite or glass opal:
Valeč, Doupov, Karlovy Vary, Bohemia, Czech Republic
Although Bohemia includes quite a few sites where uranium minerals are found, Hyalite from Valeč is not really famous for its strong green fluorescence. It is, however, well known for its beautiful botryoidal appearance. MKA-member, Raymond Dedeyne, is one of those serious collectors who wants to know all there is about such fine specimens. He was quite surprised about the strong fluorescence of his hyalite specimen and asked me to find out what was causing it. Click on the prism icon for a spectrum and explanation.
While I was working on Raymond’s specimen, I couldn't resist photographing it under different light sources. The close-up shows how exceptionally clear and well formed the opal spheres are. Each sphere works as a lens in which you can see a distorted image of the underlying rock. The fluorescence was photographed in short wave UV. Finally, I found the specimen "challenging" enough to try a technique on it that I learned from art photographer Johan Buelens. This is just an aesthetic exposure with two different colors of light and has nothing to do with fluorescence.
Gibbsite: Chenzou, Hunan provincie, China.
Exact locality probably: Xianghualing Sn-polymetallic ore field, Linwu Co., Chenzhou Prefecture, Hunan Province, China
Fluorescence due to contamination with UO22- (uranyl-ion)
http://www.mindat.org/loc-159397.html
Corundum var. ruby. Sivec Marble quarry, Sivec Mountain, Prilep, Republic of Macedonia (Kor241).
Fluorescence in long wave UV.
Activator red fluorescence: Cr3+ replacing Al3+
Activator orange fluorescence: unknown (but see spectrum)
http://www.mindat.org/min-3729.html
Spinel, Luc Yen, Yenbai Province, Vietnam.
Fluorescence in long wave UV.
Activator red fluorescence: Cr3+ replacing Al3+
Resp. in normal light and in LW & MW UV.
Spherical concretions of quartz. These specimens were found during road works in La Sassa. Quartz from this location is often misidentified as forsterite or even wavellite. However, the emission spectrum is usually identical to that of this typical Quartz.
Photos Axel Emmermann, Collection: Raymond Dedeyne
Gibbsite
Corundum var. ruby
Spinel
Quartz
Hyalite or glass-opal
