Jachymovite

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Jachymovite
General and classification
other names

IMA 1994-025

chemical formula [(UO 2 ) 8 | (OH) 14 | SO 4 ] • 13H 2 O
Mineral class
(and possibly department)
Sulfates (including selenates, tellurates, chromates, molybdates, and tungstates)
System no. to Strunz
and to Dana
7.EA.10 ( 8th edition : VI / D.20)
02/31/06/02
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic sphenoid or prismatic; 2 or 2 / m
Room group (no.) P 2 1 or P 2 1 / m (No. 4 or 11)
Lattice parameters a  = 18.55  Å ; b  = 9.28 Å; c  = 13.53 Å
β  = 125.6 °
Formula units Z  = 2
Physical Properties
Mohs hardness not defined
Density (g / cm 3 ) calculated: 4.79
Cleavage very good after {010}
Break ; Tenacity clamshell; brittle
colour yellow
Line color light yellow
transparency translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.715
n β  = 1.718
n γ  = 1.720
Birefringence δ = 0.005
Optical character biaxial negative
Axis angle 2V = calculated: 78 °
Other properties
Special features yellow fluorescence

Jáchymovite is a very rarely occurring mineral from the mineral class of "sulfates (including selenates, tellurates, chromates, molybdates and tungstates)". It crystallizes in the monoclinic crystal system with the chemical composition [(UO 2 ) 8 | (OH) 14 | SO 4 ] · 13H 2 O, so it is a water-containing uranyl sulfate with additional hydroxide ions .

Jáchymovite is translucent and has so far only been found in the form of crusty coatings of needle-like, about 0.1 millimeter long crystals of yellow color with light yellow streak color . The crystal surfaces show a glass-like sheen .

Etymology and history

Jáchymovite was first discovered in a museum on a mineral sample from Jáchymov in the Czech region of Bohemia with strongly oxidized, uraninite-containing veins in dolomite . The mineral was described in 1996 by Jiří Čejka, Jiří Sejkora, Z. Mrazek, Z. Urbanec and T. Jarchovky, who named it after the location of the mineral sample ( type locality ).

The type material of the mineral is kept in the Natural History Museum in Prague in the Czech Republic (catalog no. P1N-68905).

The uranyl sulfate jachymovite should not be confused with the basic copper uranyl silicate cuprosklodovskite, which was formerly synonymous with jachymovite .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the jáchymovite belonged to the mineral class of "sulphates (including selenates, tellurates, chromates, molybdates and tungstates)" and there to the department of "hydrous sulphates with foreign anions ", where he together with Cobaltzippeit , Uranopilite , Magnesiumzippeit , Marécottit , Metauranopilit , Natrozippeit , Nickelzippeit , Rabejacit , Zinkzippeit and Zippeit the "Uranopilite group" VI / D.20 formed.

In contrast , the 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), classifies Jáchymovite in the “uranyl sulfate” department. This is further subdivided according to the possible presence of cations and their relative size, so that the mineral can be found according to its composition in the sub-section "Without cations", where it is the only member of the unnamed group 7.EA.10 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Jáchymovite to the class of "sulfates, chromates and molybdates" and there in the category of "water-containing sulfates with hydroxyl or halogen". Here it can be found together with Uranopilit in the unnamed group 02/31/06 within the sub-section “ Hydrogen sulfates with hydroxyl or halogen with (A + B 2+ ) 6 (XO 4 ) Z q × x (H 2 O)”.

Crystal structure

Jáchymovit crystallizes monoclinically in the space group P 2 1 (space group no. 4) or P 2 1 / m (space group no. 11) with the lattice parameters a  = 18.55  Å ; b  = 9.28 Å; c  = 13.53 Å and β = 125.6 ° and two formula units per unit cell .

properties

The mineral is very radioactive due to its uranium content of up to 69.79% . Taking into account the natural series of decay or existing decay products, the specific activity is given as 124.921 k Bq / g (for comparison: natural potassium 0.0312 kBq / g).

Under UV light , some Jáchymovites show a yellow fluorescence , similar to that of neon-colored highlighters .

Education and Locations

Jáchymovite is so far only known in a few samples from three sites (as of 2014). Besides its type locality Jáchymov, the mineral was in the Czech Republic only in a uranium ore - deposit near Horni Slavkov be found (Bohemia). Jáchymovite was also found in the uranium prospecting "La Creusaz" near Les Marécottes in the Le Trient valley in the Swiss canton of Valais.

Precautions

Due to the strong radioactivity of the mineral, mineral samples from Jáchymovite should only be kept in dust- and radiation-tight containers, but especially never in living rooms, bedrooms or workrooms. Absorption into the body ( incorporation , ingestion ) should also 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

  • Jiří Čejka, Jiří Sejkora, Z. Mrazek, Z. Urbanec, T. Jarchovky (1996): Jáchymovite, (UO 2 ) 8 (SO 4 ) (OH) 14 · 13H 2 O, a new uranyl mineral from Jáchymov, the Krusne Hory Mts., Czech Republic, and its comparison with uranopilite. In: New Yearbook for Mineralogy, Treatises. Volume 170, pp. 155-170
  • Jiří Čejka, Ray L. Frost, Jiří Sejkora, Eloise C. Keeffe (2009): Raman spectroscopic study of the uranyl sulphate mineral jáchymovite (UO 2 ) 8 (SO 4 ) (OH) 14 13H 2 O. In: Journal of Raman Spectroscopy. Volume 40 (11), pp. 1464–1468 ( PDF 248 kB )

Web links

Individual evidence

  1. a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X .
  2. a b c Jáchymovite , 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 )
  3. a b c Mindat - Jáchymovite
  4. Webmineral - Jáchymovite
  5. Find location list for Jáchymovite in the Mineralienatlas and in Mindat