Arsenuranospathite
| Arsenuranospathite | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.EB.25 ( 8th edition : VII / E.04) 40.02a.23.01 |
| Similar minerals | Uranospathite |
| Crystallographic Data | |
| Crystal system | unexplained |
| Crystal class ; symbol | tetragonal-dipyramidal; 4 / m (possibly orthorhombic and pseudotetragonal) |
| Space group | P 4 2 / n (No. 86) |
| Lattice parameters |
a = 7.280 Å ; b = 7.280 Å; c = 20.73 Å α = 90 °; β = 90 °; γ = 90 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | 2.54 |
| Cleavage | perfect according to {001}, good according to {100} and {010} |
| colour | colorless, pale yellow, yellow, yellow-brown, brown |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| radioactivity | highly radioactive |
| Crystal optics | |
| Birefringence | δ = 0.004 |
| Optical character | uniaxial negative |
| Axis angle | 2V = 52 ° |
| Other properties | |
| Special features | dehydrated at room temperature; faint greenish fluorescence under UV light of variable intensity |
Arsenuranospathite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the tetragonal crystal system (but may orthorhombic and pseudotetragonal) with the chemical composition HAl (UO 2 ) 4 (AsO 4 ) 4 · 40H 2 O and is chemically a hydrous aluminum - uranyl - arsenate . The mineral often develops latte-like, pale yellow to brown crystals .
Etymology and history
Arsenuranospathite was first described in 1959 by Kurt Walenta on a mineral sample from Menzenschwand . Walenta called the mineral arsenuranospathite because of its arsenic content and its similarity to uranospathite .
classification
Already in the now obsolete but still in use 8th edition of the mineral classification by Strunz of Arsenuranospathit belonged to the mineral class of "phosphates, arsenates, vanadates" and then to the Department of "uranyl phosphates and Uranylvanadate" where he along with Uranospathit the unnamed group VII / E.04 made.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns arsenuranospathite to the class of "phosphates, arsenates and vanadates" and there in the department of "uranyl phosphates and arsenates". This section is further subdivided according to the molar ratio of uranium oxide complex (UO 2 ) and phosphate or arsenate complex (RO 4 ), so that the mineral can be found in the sub-section "UO 2 : RO 4 = 1: 1" according to its composition , where together with uranospathite the "uranospathite group" with the system no. 8.EB.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the arsenuranospathite to the class of "phosphates, arsenates, vanadates", but there in the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is the only member of the unnamed group 40.02a.23 within the subdivision of “ Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O), with (UO 2 ) 2+ ”.
Crystal structure
Arsenuranospathite crystallizes tetragonally in the space group P 4 2 / n (space group no. 86) with the lattice parameters a = 7.28 Å , b = 7.28 Å and c = 20.73 Å as well as two formula units per unit cell . So far (as of August 2014) only the data published by Walenta on uranospathite are available. He himself suspects that the mineral is merely pseudo-tetragonal and, like uranospathite, actually orthorhombic; however, this has not yet been verified. A single crystal structure analysis is still missing.
properties
The mineral is radioactive due to its uranium content of up to 39.9% . Taking into account the proportions of radioactive elements in the idealized empirical formula as well as the subsequent decays of the natural decay series, a specific activity of about 71.5 k Bq / g is specified for the mineral (for comparison: 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.
In a dry environment, arsenuranospathite converts to HAl (UO 2 ) 4 (AsO 4 ) 4 · 20H 2 O , releasing part of its water of crystallization . This process is reversible if the mineral is exposed to a cold, humid atmosphere immediately after dehydration . After a long period of time in the dehydrated state, the process is irreversible.
Under UV light , arsenuranospathite shows a weak greenish fluorescence with varying intensity.
Education and Locations
Arsenuranospathite forms as a secondary mineral in the oxidation zone of uranium deposits . It occurs barite and in paragenesis with limonite , Zeunerit , Uranophan , studtite and mixed crystals of Uranocircit - Heinrichit on. Other accompanying minerals are uranospathite , metakirchheimerite , uranospinite and ianthinite .
Arsenuranospathite occurs only very rarely worldwide. In Germany , the mineral from the Krunkelbach mine near Menzenschwand and from the Sophia mine near Wittichen is known. Other locations are Schnellingen and St. Ulrich, as well as the Bühlskopf uranium deposit in Ellweiler . In Switzerland it is known from La Creusaz in the canton of Valais . The only other known sites are Rabejac near Lodève in the Hérault department in the Occitania region and the Les Sagnes mine near Razès and La Crouzille near Saint-Sylvestre in the Haute-Vienne department in the Nouvelle-Aquitaine region , the Bota-Burum deposit on Lake Alaköl in Kazakhstan and Jáchymov in the Czech Republic .
Precautions
Due to the toxicity and the strong radioactivity of the mineral, mineral samples of arsenurane phosphite should only be kept in dust- and radiation-tight containers, but especially never in living rooms, bedrooms or work rooms. Absorption into the body (incorporation, ingestion ) should also be prevented in any case and, for safety, direct body contact should be avoided and respiratory protection mask and gloves should be worn when handling the mineral .
See also
literature
- Thomas Theye, Kurt Walenta, Gregor Markl: The chemical composition of uranospathite, arsenuranospathite, and associated minerals revisited: the peculiarity of fluorine incorporation in autunite group minerals . In: New Yearbook for Mineralogy - Treatises . tape 193 , no. 1 , 2016, p. 59–68 , doi : 10.1127 / njma / 2015/0292 .
- Arsenuranospathites . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 63 kB ; accessed on April 12, 2018]).
Web links
Remarks
- ↑ This is the conventional notation with integer formula indices.
Individual evidence
- ↑ a b c d e f g h i j k l m n o p Kurt Walenta: Uranospathite and arsenuranospathite. In: Mineralogical Magazine , Volume 42, March 1978, pp. 117–128 ( PDF 857 kB , English)
- ↑ a b c Webmineral - Arsenuranospathite (English)
- ↑ RRUFF Database-of-Raman spectroscopy - Arsenuranospathit
- ↑ a b c Mindat - Arsenuranospathite (English)