Curit
| Curit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Pb 3 [(UO 2 ) 4 | O 4 | (OH) 3 ] 2 · 2 H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.GB.55 ( 8th edition : IV / H.07) 09/05/03/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pnam (No. 62) |
| Lattice parameters | a = 12.56 Å ; b = 13.02 Å; c = 8.40 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {100}, {110}, {111} |
| Physical Properties | |
| Mohs hardness | 4 to 5 |
| Density (g / cm 3 ) | measured: 6.98 to 7.4; calculated: 7.37 |
| Cleavage | after {100} |
| Break ; Tenacity | uneven; brittle |
| colour | yellow-orange to red-orange |
| Line color | orange |
| transparency | transparent to opaque |
| shine | Diamond shine, earthy |
| radioactivity | very radioactive |
| Crystal optics | |
| Refractive indices |
n α = 2.060 n β = 2.110 n γ = 2.150 |
| Birefringence | δ = 0.090 |
| Optical character | biaxial negative |
| Axis angle | 2V = 70 ° (measured); 80 ° (calculated) |
| Pleochroism | visible: X = b = light yellow Y = a = light red-orange Z = c = dark red-orange |
Curit is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition Pb 3 [(UO 2 ) 4 | O 4 | (OH) 3 ] 2 · 2 H 2 O and develops mostly granular to massive or earthy mineral aggregates or crusty coatings, rarely also needle-like crystals from yellow-orange to red-orange color.
Etymology and history
Curit was first found in the " Shinkolobwe Mine (Kasolo Mine)" in Katanga in the Democratic Republic of the Congo and described in 1921 by Alfred Schoep (1881–1966). The mineral is named after the physicist and Nobel Prize winner Pierre Curie (1859–1906).
classification
In the old classification of minerals by Strunz (8th edition) of Curit yet for the joint department of "uranyl hydroxides and hydrates" is one where with he together Fourmarierit , Metavandendriesscheit , Richetit , Sayrit , Spriggit and Vanden Dries log forms an independent group.
With the revision of Strunz's mineral classification in the 9th edition , this department was divided up and also more precisely divided according to the type of cations involved and the crystal structure. The mineral is now in the “Uranyl Hydroxide” department and there as the only one in its group in the “With additional cations (K, Ca, Ba, Pb etc.) and predominantly UO 2 (O, OH) 5 pentagonal polyhedra “With the system number 4.GB.55.
The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns curit to the class of oxides and hydroxides, but there in the division of " uranium and thorium-containing oxides with a cation charge of 6+, Pb or Bi and some water of hydration or hydroxyl included ".
Crystal structure
Curit crystallizes orthorhombically in the space group Pnam (space group no. 62) with the lattice parameters of about a = 12.56 Å determined in several measurements from the year 2000 ; b = 13.02 Å and c = 8.40 Å as well as two formula units per unit cell .
The crystal structure consists of layers of edge and corner linked uranyl polyhedra , the uranyl cation having both pentagonal-bipyramidal and square-bipyramidal (octahedral) coordination. The lead atoms link these layers by coordinating the uranyl oxygen atoms.
properties
The mineral is classified as very radioactive due to its uranium content of over 63% . 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 113.4 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
Curite is a secondary mineral that is formed by weathering geologically old uraninite . This is due to the formation of lead due to radioactive decay. Curit eventually forms in the oxidation zone of ore deposits or in crevices of sedimentary rocks . Accompanying minerals include dewindtite , fourmarierite , kasolite , rutherfordine , schoepite , soddyite , slodovskite , torbernite and vandendriesscheit .
In addition to its type locality "Shinkolobwe Mine (Kasolo Mine)" in the Democratic Republic of the Congo, Curit has been detected at around 50 sites worldwide so far (as of 2009), including in "Dara-Um Swassi" in the northeastern desert on the Red Sea in Egypt; Northern Territory of Australia; Baden-Württemberg , Bavaria , Rhineland-Palatinate and Saxony in Germany; Auvergne , Brittany , Alsace and Limousin in France; Lombardy and Trentino-South Tyrol in Italy; in the Northwest Territories of Canada; at Fianarantsoa in Madagascar; Aust-Agder and Telemark in Norway; in the Russian region of Karelia ; Namaqualand in South Africa; Bohemia and Moravia in the Czech Republic; in the Hungarian counties of Baranya and Heves and in the US regions of Colorado , New Hampshire and New Mexico .
Precautions
Due to the strong radioactivity of the mineral, mineral samples from Curit 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
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 560 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 111 .
Web links
- Mineral Atlas: Curit (Wiki)
- Photos by Curit on the website of the Association des Géologues Amateurs de Belgique (AGAB)
Individual evidence
- ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ a b c d Webmineral Curite (English)
- ↑ a b c American Mineralogist Crystal Structure Database ( AMCSD - Curite ) (English, 2000)
- ↑ a b c Curite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF (English) 69 kB )
- ↑ a b c Mindat Curite (English)
- ↑ A. Schoep: La curite, nouveau minéral radioactif In: Comptes Rendus Hebdomadaires of séances de l'Académie des Sciences in 1921, 173 , 1186-1187. ( PDF (French) 91.6 kB )
- ↑ a b Y. Li, PC Burns: Investigations of crystal-chemical variability in lead uranyl oxide hydrates. I. CURITE , In: The Canadian Mineralogist 2000, Vol. 38 , pp. 727-735. ( PDF (English) 363.2 kB )
- ↑ Find location list for Curit at the Mineralienatlas and at Mindat