Kahlerite

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Kahlerite
General and classification
chemical formula Fe 2+ [UO 2 | AsO 4 ] 2 · 10-12H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.EB.05 ( 8th edition : VII / E.01)
40.02a.15.01
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol tetragonal-dipyramidal; 4 / m
Room group (no.) P 4 2 / n (No. 86)
Lattice parameters a  = 14.3  Å ; c  = 21.97 Å Please complete the source as an individual reference!
Formula units Z  = 8 Please complete the source as an individual reference!
Physical Properties
Mohs hardness 2 to 3
Density (g / cm 3 ) calculated: 3.22
Cleavage Please complete!
colour lemon yellow, yellow green
Line color light yellow
transparency transparent to translucent
shine Glass gloss
radioactivity highly radioactive
Crystal optics
Refractive indices n ω  = 1.634
n ε  = 1.632
Birefringence δ = 0.002
Optical character uniaxial negative
Axis angle 2V = 9 to 33 °
Other properties
Chemical behavior very poisonus

Kahlerite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the tetragonal crystal system with the chemical composition Fe 2+ [UO 2 | AsO 4 ] 2 · 10-12H 2 O and develops mostly transparent to translucent, thin-tabular crystals up to about 2 mm in size from lemon-yellow to yellow-green color and light yellow streak color .

Etymology and history

Kahlerite was first discovered in 1953 on the Hüttenberger Erzberg in Carinthia by Heinz Meixner , who named the mineral in honor of the Austrian geologist Franz Kahler .

classification

In the meanwhile outdated, but still in use 8th edition of the systematics of minerals according to Strunz , the kahlerite still belongs to the general section of "uranyl phosphates and uranyl vanadates".

However, since the 9th edition of Strunz's mineral systematics was restructured in 2001, this department has been redefined and more precisely divided according to chemical composition. Accordingly, the mineral can now be found in the subdivision of "uranyl phosphates and arsenates with the molar ratio uranium oxide complex (UO 2 ): phosphate or arsenate complex (RO 4 ) = 1: 1 of the autunit family with [(UO 2 ) -RO 4 ]" -Locations ". There it forms together with Autunit , Heinrichit , Kirchheimerit , Nováčekit-I , Nováčekit-II , Saléeit , Torbernit , Uranocircit I , Uranocircite II , Uranospinit , Xiangjiangit and Zeunerit the unnamed group 8.EB.05 .

The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns kahlerite to the class of "phosphates, arsenates, vanadates", but there in the department of hydrated phosphates etc., with the general composition A ++ (B ++ ) 2 (XO 4 ) • (H 2 O), with (UO 2 ) ++ , where together with metakahlerite it forms its own group with the designation 40.2a.15 .

Crystal structure

Kahlerite crystallizes tetragonally in the space group P 4 2 / n (space group no. 86) with the lattice parameters a  = 14.3  Å and c  = 21.97 Å and 8 formula units per unit cell .

properties

The mineral is very toxic due to its arsenic content and highly radioactive due to its uranium content of up to 44.41% with a specific activity of about 79.5 k Bq / g (for comparison: natural potassium 31.2 Bq / g).

Education and Locations

Kahlerite forms as a rare secondary mineral in the oxidation zone of iron-bearing uranium deposits . Begleitminerale include Arseniosiderit , Cornubit , Lavendulan , Löllingit , malachite , Metakahlerit , Metazeunerit , Mixit , Pitticit , Skorodit , Symplesit , Tyrolit , Wulfenit and Zeunerit .

So far (as of 2010) the mineral has been found at around 10 sites around the world: in Austria as a type locality on the " Hüttenberger Erzberg " in Carinthia, as well as near Mühlbach am Hochkönig (Salzburg), near Schneeberg in Germany, near Jáchymov in the Czech Republic, near Lodève in France, in “Caulkerbush” and the “Needle's Eye Mine” in Dumfries and Galloway (Scotland) and in the “Krantzberg Mine” near Omaruru in Namibia.

Precautions

Due to the toxicity and the strong radioactivity of the mineral, mineral samples from Kahlerite 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 respiratory protection mask and gloves should be worn when handling the mineral .

See also

Individual evidence

  1. ↑ a b Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  2. ↑ a b Webmineral - Kahlerite (English)
  3. ↑ a b Kahlerite at mindat.org (engl.)
  4. ↑ Mindat - Localities for Kahlerite

Web links