| Studtite | |
|---|---|
 | |
| General | |
| Category | Oxide mineral |
| Formula | UO2O2·4(H2O) |
| IMA symbol | Stu[1] |
| Strunz classification | 4.GA.15 Uranyl hydroxides |
| Dana classification | 05.03.01.01 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (sameH-M symbol) |
| Space group | C2/m |
| Identification | |
| Color | Yellow to pale yellow; nearly colorless in transmitted light |
| Crystal habit | Needlelike crystals in radial fibrous aggregates and crusts |
| 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 |
| Ultravioletfluorescence | Non-fluorescent |
| Alters to | Dehydrates to metastudtite |
| Other characteristics |  Radioactive |
| References | [2][3][4] |
Studtite,chemical formula [(UO2)O2(H2O)2]·2(H2O)[2] or UO4·4(H2O),[3] is asecondaryuraniummineral containingperoxide formed by thealpha-radiolysis of water during formation.[5] It occurs as pale yellow to white needle-likecrystals often inacicular, white sprays.
Studtite was originally described by Vaes in 1947[6] from specimens fromShinkolobwe, 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 Englishprospector andgeologist who was working for the Belgians.
When exposed to air studtite converts over a short time to themetastudtite UO4·2(H2O) form. Despite their apparent chemical simplicity, these two uranyl species are the only reported peroxide minerals.[5]
They may also be readily formed on the surface ofnuclear waste under long-term storage and have been found on the surface of spentnuclear fuel stored at theHanford, Washington nuclear site.[7] It has also been reported that studtite has since formed on thecoriumlavas that were created during the course of theChernobyl nuclear plant accident.[7] Thus, there is considerable evidence thaturanyl peroxides such as studtite and metastudtite will be important alteration phases ofnuclear waste, possibly at the expense of other minerals, such asuranyl oxides andsilicates, which have been more thoroughly studied and are better understood. The formation of these minerals may impact the long-term performance ofdeep geological repository sites such asYucca Mountain nuclear waste repository.[7] Due to insufficient information about these minerals it is unknown if they will makeradioactive wastes more or less stable, but the presence of studtite and metastudtite provides a pathway for mobilizing insoluble U(IV) from the corroding fuel surface into solubleuranyl species.[8]
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