Studtite

Studtite
General
Category Oxide mineral
Formula
(repeating unit)		 UO4·4(H2O)
Strunz classification 04.GA.15 Uranyl hydroxides
Dana classification 05.03.01.01
Identification
Color Yellow to pale yellow; nearly colorless in transmitted light
Crystal habit Needlelike crystals in radial fibrous aggregates and crusts
Crystal system Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/m
Tenacity Flexible
Mohs scale hardness 1 - 2
Luster Vitreous, waxy
Streak Light yellow
Diaphaneity Translucent
Specific gravity 3.58
Optical properties Biaxial (+)
Refractive index nα = 1.545 nβ = 1.555 nγ = 1.680
Birefringence δ = 0.135
Ultraviolet fluorescence Non-fluorescent
Alters to Dehydrates to metastudtite
Other characteristics Radioactive
References [1][2][3]

Studtite, chemical formula [(UO2)O2(H2O)2]·2(H2O)[1] or UO4·4(H2O),[2] is a secondary uranium mineral containing peroxide formed by the alpha-radiolysis of water during formation.[4] It occurs as pale yellow to white needle-like crystals often in acicular, white sprays.

Studtite was originally described by Vaes in 1947[5] from specimens from Shinkolobwe, Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo, and has since been reported from several other localities. The mineral was named for Franz Edward Studt, an English prospector and geologist who was working for the Belgians.

When exposed to air studtite converts over a short time to the metastudtite UO4·2(H2O) form. Despite their apparent chemical simplicity, these two uranyl species are the only reported peroxide minerals.[4]

They may also be readily formed on the surface of nuclear waste under long-term storage and have been found on the surface of spent nuclear fuel stored at the Hanford, Washington nuclear site.[6] It has also been reported that studtite has since formed on the corium lavas that were created during the course of the Chernobyl nuclear plant accident.[6] Thus, there is considerable evidence that uranyl peroxides such as studtite and metastudtite will be important alteration phases of nuclear waste, possibly at the expense of other minerals, such as uranyl oxides and silicates, which have been more thoroughly studied and are better understood. The formation of these minerals may impact the long-term performance of deep geological repository sites such as Yucca Mountain nuclear waste repository.[6] Not enough is known about these minerals to know if they will make radioactive wastes more or less stable.

References

  1. ↑ 1.0 1.1 http://webmineral.com/data/Studtite.shtml Studtite at Webmineral
  2. ↑ 2.0 2.1 http://rruff.geo.arizona.edu/doclib/hom/studtite.pdf Handbook of Mineralogy
  3. ↑ http://www.mindat.org/min-3815.html Mindat.org
  4. ↑ 4.0 4.1 http://www.kubatko.com/studtitestructure.pdf Studtite: The first structure of a peroxide mineral]
  5. ↑ Annales de la Société Géologique de Belgique - 1947 - pp B212 to B226- J.F. Vaes - Six nouveaux minéraux d'urane provenant de Shinkolobwe (Katanga) -
  6. ↑ 6.0 6.1 6.2 [http://www.news.ucdavis.edu/search/news_detail.lasso?id=6810 Unusual Minerals Formed on Stored Nuclear Waste (Pub. in Nov. 14, 2003 issue of Science)
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