Zellerite

Zellerite
General
Category	Minerals
Formula	Ca(UO2)(CO3)2 · 5H2O
IMA symbol	Zel [1]
Strunz classification	5.EC.10
Dana classification	15.3.1.1
Crystal system	Orthorhombic
Crystal class	H-M symbol: 2/m 2/m 2/m or mm2
Space group	Pmmm or Pmn21
Unit cell	1,064.81
Identification
Color	White yellow, light lemon-yellow, lemon
Crystal habit	Acicular
Cleavage	One
Mohs scale hardness	2
Luster	Dull
Streak	White
Diaphaneity	Transparent, translucent
Specific gravity	3.25
Density	3.25
Optical properties	Biaxial (+)
Refractive index	nα = 1.536 nβ = 1.559 nγ = 1.697
Birefringence	0.161
2V angle	Measured: 30°- 45° Calculated: 48°
Dispersion	Weak r > v
Ultraviolet fluorescence	SW and LW Green patches
Other characteristics	Radioactive

Zellerite is a uranium mineral, named after its discoverer, geologist Howard Davis Zeller. It has a type locality of the Lucky MC uranium mine in Wyoming, USA. It was approved by the IMA in 1965, but was first published a year after its approval. ^[2]

Properties

Zellerite is a dimorph of meyrowitzite. It is a uranyl carbonate. ^[2] It is an acicular mineral, and occurs in crystals that resemble the shape of needles. ^[3] It can occur as fine hairlike fibers as well. The size of each crystal is up to 2 mm, and it grows in roughly radial aggregates, veinlets, and incrustations. Elongation is possible. ^[4] It has pleochroic attributes, which is an optical phenomenon. Depending on which axis the specimen is being inspected, it can occur as it changes color. Upon being inspected on the x or y axis, the mineral can seem to be colorless, but on the z axis, it is seen in a pale yellow color. The mineral also shows luminescence. Under both a short wave and a long wave ultraviolet light, it fluoresces in green patches. ^[2] , which is typical for Uranium compounds. The fully hydrated form of the mineral is lemon yellow, but in transmitted light, it has a very pale yellow color. The dehydrated version of the mineral is called metazellerite.

Zellerite is also radioactive: the concentration of the mineral per Gamma Ray American Petroleum Institute Units is 280.20, due to it consisting of 45.76% uranium. The remaining constituents are oxygen (39.98%), calcium (7.70%), carbon (4.62%) and hydrogen (1.94%). ^[3] This rare mineral forms in the weathering zone as an oxidation product of uraninite-coffinite, in the presence of an oxidizing pyrite, where the pH is greater than 7 and the partial pressure of carbon dioxide is greater than the atmosphere's. It is associated with metazellerite, gypsum, uranophane, meta-autunite, schoepite, iron sulfides, limonite and opal. ^[4]

References

1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
2. "Zellerite". www.mindat.org. Retrieved 2021-09-24.
3. "Zellerite Mineral Data". webmineral.com. Retrieved 2021-09-24.
4. Coleman, R. G.; Ross, D. R.; Meyrowitz, R. (1966-12-01). "Zellerite and metazellerite, New Uranyl Carbonates1". American Mineralogist. 51 (11–12): 1567–1578. ISSN   0003-004X.