Haynesite

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Haynesite
Haynesite.jpg
Yellow, radial-radial aggregates of haynesite on mudstone from the type locality , Repete Mine, San Juan Co., Utah, USA. (Image width: 2.9 mm)
General and classification
chemical formula (UO 2 ) 3 (OH) 2 (SeO 3 ) 2 O 2 • 5H 2 O
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.JJ.25 ( 8th edition : IV / K.11)
07/34/07/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic mm 2 or mmm
Room group (no.) (No. 30, 53)
Lattice parameters a  = 8.025 (5)  Å ; b  = 17.43 (1) Å; c  = 6.935 (3) Å Please complete the source as an individual reference!
Formula units Z  = 2 Please complete the source as an individual reference!
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) 4.1
Cleavage good after {010}
colour brownish yellow, amber colored
Line color White
transparency transparent to translucent
shine Glass gloss
radioactivity very strong
Crystal optics
Refractive indices n α  = 1.618
n β  = 1.738
n γ  = 1.765
Birefringence δ = 0.147
Optical character biaxial negative
Axis angle 2V = 45 ° (measured); 10 ° (calculated)
Pleochroism X = pale yellow; Y = Z = light yellow
Other properties
Special features yellow-green fluorescence under short-wave UV light

Haynesit is a very rare occurring uranium - mineral from the mineral class of "oxides and hydroxides" (including V [5,6] -Vanadate, Arsenites, Antimonite, Bismutite, sulfites, Selenite, tellurites and iodates). It crystallizes in the orthorhombic crystal system with the chemical composition (UO 2 ) 3 (OH) 2 (SeO 3 ) 2 O 2 · 5H 2 O, is thus a basic water-containing uranyl - selenite .

Haynesite often develops needle-like, brownish-yellow to amber-colored crystals and yellow aggregates. So far, it is known from only one site worldwide.

Etymology and history

Haynesite was first discovered in 1991 in a mineral sample from the Repete Mine near Blanding in San Juan County , Utah , and was first described by Michel Deliens and Paul Piret . They named the mineral after the geologist Patrick Eugene Haynes (* 1953), who found the first mineral samples of haynesite.

The type mineral is located in the Museum of Natural Sciences in Brussels .

classification

The outdated 8th edition of Strunz lists the haynesite under "Uranylselenite with assemblies [UO 2 ] 2+ to [SeO 3 ] 2− " with the system no. IV / K.11 together with Demesmaekerit , Derriksit , Guilleminit , Larisait , Marthozit and Piretit .

The 9th, completely revised edition of Strunz lists the haynesite in section J " Selenite with additional anions, with H 2 O " as the only representative of the group 4.JJ.25 .

The systematics of minerals according to Dana , which is common in the English-speaking world , classifies the haynesite under the selenites - tellurites - sulphites within the sulphates, chromates and molybdates with the system number. 34.07.0.01 a.

Crystal structure

Haynesite crystallizes orthorhombically in the space group Pnc 2 or Pncm with the lattice parameters a  = 8.025 (5)  Å ; b  = 17.43 (1) Å; c  = 6.935 (3) Å and 2 formula units per unit cell .

properties

The mineral is radioactive due to its uranium content of up to 60.1% . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the Folgezerfälle of the natural decay chains a specific activity of about 107 K for the mineral Bq stated / g (compared to natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and the composition of the levels; selective enrichment or depletion of the radioactive decay products is also possible and changes the activity.

Education and Locations

Haynesite forms as a secondary uranium mineral in the oxidation zone of selenium-rich hydrothermal uranium ores. It is found associated with andersonite , boltwoodite , gypsum and calcite on claystone and sandstone . So far it is only known from its type locality , the Repete Mine in Utah. The mine has been closed since 1987.

Precautions

Due to the strong radioactivity of the mineral, mineral samples from haynesite should only be kept in dust- and radiation-tight containers, but above all never in living rooms, bedrooms or work rooms. Likewise, because of the high toxicity and radioactivity of uranyl compounds, absorption into the body ( incorporation , ingestion ) should be prevented in any case and, for safety, direct body contact should be avoided and face masks and gloves should be worn when handling the mineral.

See also

literature

  • Haynesite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.8 kB )

Web links

Commons : Haynesit  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d M. Deliens, P. Piret: La haynesite, sélénite hydraté d'uranyle, nouvelle espèce minérale de la Mine Repete, Comté de San Juan, Utah. In: The Canadian Mineralogist 1991, 29, pp. 561-564. ( PDF, 417 kB (French) )
  2. ↑ a b c d e Haynesite at Webmineral.com
  3. ^ Mindat - Haynesite
  4. ↑ Patrick E. Haynes: Metamunirite, haynesite, and other microminerals from the four-corners states In: New Mexico Mineral Symposium, November 9-10, 1991. online