Wednesday, December 9, 2020

Uranium van Gogh

 My favorite ☢️ specimen during an otherwise not-so-good year. This mineral exhibits awesome green crystals and it is named after one of the greatest female scientists.

Cuprosklodowskite and Sklodowskite

Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of the Congo

"Sunflowers" (medium: Crystals on Matrix)
If Uranium learned to paint from Vincent van Gogh - post-impressionism style...

A gorgeous specimen, with two main cavities, 15 mm across, richly lined with luminous green Cuprosklodowskite, turning to yellow Sklodowskite closer to the Uraninite matrix.

Size is 2.8 × 4.9 × 3.5 cm with largest crystals around 5mm

The rock, I affectionally call "Marie" is quite "hot" - at 1" (2.54cm) it measures over 508 000 CPM with my LND7317-based counter (if I have the "dead time" GM tube constant set correctly). This is approximately 145 mR/hr or 1.45 mSv/hr! 
I noticed a direct correlations between the "looks" of a specimen and its activity when it comes to Uranium minerals - the prettiest looking ones are usually also the most active :-)

Crystal tufts of Sklodowskite (Mg(UO2)2(HSiO4)2·5(H2O)) stem from the Uraninite infused matrix and transition into Cuprosklodowskite (Cu(UO2)2(HSiO4)2·6(H2O))

One of the two cavities densely populated with crystals.

Activity for this mineral is quite high - Sklodowskite has a calculated activity of 99.244 KBq/gram and exposure of 1.38 mRem/hr for 1 gram when held in hand. Considering that it also contains Uraninite with even higher activity it is definitely one of the specimen requiring caution when handling and storage.
2.4 kg pure Sklodowskite specimen will give you the 3.6 R/hr exposure - "not great, not terrible"

Earth Archives card about the Cuprosklodowskite.

 Another Cuprosklodowskite from the same locality - Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of the Congo
The specimen exhibits interweave of shiny, glassy bright-green "sturdy" acicular crystals of Cuprosklodowskite.

Yet another Cuprosklodowskite and Uraninite. Same locality as the other above.
This specimen has a bright green area of microcrystals and a black uraninite crude crystal on a base of gummite matrix.
Cuprosklodowskite in general is a very active mineral and the Uraninite crystal just adds to this - measured activity is around 150 000 CPM @ 5 mm.

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