Znucalite

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Znucalite
Znucalite.jpg
Colorless Znucalite from Příbram, Czech Republic (image width approx. 10 mm)
General and classification
other names

IMA 1989-033

chemical formula
  • First description:

Zn 12 (UO 2 ) Ca (CO 3 ) 3 (OH) 22 4 (H 2 O)

CaZn 12 [UO 2 | (OH) 22 | (CO 3 ) 3 ] • 4H 2 O

  • IMA:

CaZn 11 (UO 2 ) (CO 3 ) 3 (OH) 20 · 4H 2 O

Mineral class
(and possibly department) 		Carbonates and nitrates
System no. to Strunz
and to Dana 		5.ED.45
16b.07.14.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol not defined
Lattice parameters a  = 10.72 (1)  Å ; b  = 25.16 (1) Å; c  = 6.325 (4) Å
Formula units Z  = 2
Physical Properties
Mohs hardness not defined
Density (g / cm 3 ) measured: 3.01-3.1; calculated: 3.15
Cleavage completely after {010}
colour colorless to pale greenish yellow
Line color White
transparency translucent
shine Silky gloss
radioactivity very strong
Crystal optics
Refractive indices n α  = 1.563
n β  = 1.621
n γ  = 1.621
Birefringence δ = 0.058
Optical character biaxial negative
Axis angle 2V = 50 ° to 66 ° (measured)

Znucalit is a very rare mineral from the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates ). It crystallizes in the orthorhombic crystal system with the chemical composition CaZn 11 (UO 2 ) (CO 3 ) 3 (OH) 20 · 4H 2 O and is therefore a basic calcium - zinc - uranyl carbonate , one of the uranyl compounds .

Znucalit only develops microscopic, colorless to pale yellow crystals between 15 × 8 × 0.4 and up to 350 micrometers in diameter. It is usually found in the form of thin, crusty coatings with a silk-like sheen on the surfaces. Znucalite is known from only six regions worldwide and is one of the few practically colorless uranium minerals.

Etymology and history

Znucalite was first discovered in 1989 on an overburden dump in the Lill mine, which was operated in the second half of the 19th century near Příbram in what is now the Czech Republic. It was named after the composition of its cations Zn ( zinc ), U ( uranium ) and Ca ( calcium ).

The discoverers of the mineral gave Zn 12 Ca [UO 2 | (CO 3 ) 3 (OH) 22 ] · 4 (H 2 O) as the molecular formula and determined the crystal system to be triclinic . Investigations on a Znucalite sample from Mas d'Alary near Lodève in France come to the conclusion that the empirical formula Zn 11 Ca [UO 2 | (CO 3 ) 3 (OH) 20 ] · 4 (H 2 O) and that Crystal system is orthorhombic .

classification

Since Znucalite was only recognized as an independent mineral in 1989, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . Only in the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , was the mineral given the system and mineral number. V / F.03-15 . In the "lapis Classification", this corresponds to the class of "nitrates, carbonates and borates" and then the department "uranyl carbonate [UO 2 ] 2+ - [CO 3 ] 2- " where Znucalit together with Roubaultit and Voglit an independent, but unnamed group forms (as of 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, assigns znucalite to the newly defined class of "carbonates and nitrates" (the borates form a separate class here), but there also in the department of "uranyl carbonates". However, this is further subdivided according to the molar ratio of uranyl (UO 2 2+ ) to carbonate complex ( CO 3 2- ), so that the mineral can be found in the sub-section "UO 2  : CO 3  = 1: 4" according to its composition where it is the only member of the unnamed group 5.ED.45 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , classifies the znucalite as the lapis systematics in the common class of "carbonates, nitrates and borates" and there in the division and subdivision of the same name of "carbonates - hydroxyl or halogen". Here he can be found as the only member in the unnamed group 16b.07.14 .

Crystal structure

Znucalite crystallizes orthorhombically with the molecular formula Zn 11 Ca [UO 2 | (CO 3 ) 3 (OH) 20 ] · 4 (H 2 O). However, the authors were only able to carry out a partial single crystal analysis, so that only the lattice parameters with a  = 10.72 (1)  Å ; b  = 25.16 (1) Å and c  = 6.325 (4) Å can be given.

The first publication ascribes the znucalite a triclinic symmetry of the empirical formula Zn 12 Ca [UO 2 | (CO 3 ) 3 (OH) 22 ] · 4 (H 2 O). The lattice parameters for this analysis are: a  = 12.692 (4)  Å ; b  = 25.096 (6) Å; c  = 11.685 (3) Å; α = 89.08 (2) °; β = 91.79 (2) ° and γ = 90.37 (3) °.

properties

The mineral is classified as very radioactive due to its uranium content of up to 14.7% and has a specific activity of around 26.274 k Bq / g (for comparison: natural potassium 31.2 Bq / g).

Education and Locations

Spherical, light yellow Znucalite aggregate from the St. Christoph pit, Bärenhecke , Saxony (image width 4 mm)

Znucalite forms as a rare secondary mineral in carbonate- containing polymetallic veins and in the vicinity of oxidizing uranium veins . The accompanying minerals include aragonite , calcite , galena , gypsum , hydrozincite , pyrite , romanite , serpierite and sphalerite .

A total of eight sites for Znucalite from six regions in five countries have been documented worldwide (as of 2020):

  • In addition to the type locality in the Czech Republic , the Lill Mine in the Březové Hory (Birkenberg) region in the Příbram district , it was also found on the spoil dump of uranium mine No. 16 in Háje and in the Svornost Mine (unity mine) near Jáchymov .
  • In Germany, Znucalite has so far only been found in the Uranus mine near Kleinrückerswalde in the Annaberg-Buchholz mining area and in the St. Christoph mine in the Bärenhecke district of Glashütte in Saxony.
  • It is known from France from Mas d'Alary near Lodève , where other accompanying minerals adamin , metalodèvite , umohoite , calcurmolite , uranophane and studtite were found.
  • In Europe it is otherwise only known from the Les Esserts Gorge in Valais in Switzerland.
  • Outside of Europe it is only known from the Sterling Mine near Ogdensburg in New Jersey, USA.

Precautions

Due to the toxicity and the strong radioactivity of the mineral, mineral samples of Znucalit should only be kept in dust- and radiation-proof 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

  • P. Ondruš, F. Veselovský, R. Rybka: Znucalite, Zn 12 (UO 2 ) Ca (CO 3 ) 3 (OH) 22 · 4H 2 O, a new mineral from Príbram, Czechoslovakia . In: New yearbook for mineralogy, monthly books . 1990, p. 393-400 (English).
  • P.-J. Chiappero, H. Sarp: Nouvelles données sur la znucalite et seconde occurrence: Le Mas d'Alary, Lodève (Hérault, France) . In: Archives des Sciences Genève . tape 46 , 1993, pp. 291-301 (French).

Web links

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

Individual evidence

  1. ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: July 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, July 2020, accessed August 30, 2020 .
  2. ^ A b c John L. Jambor, Jacek Puziewicz: New Mineral Names . In: American Mineralogist . tape 76 , 1991, pp. 1728–1735 (English, rruff.info [PDF; 753 kB ; accessed on August 30, 2020]).
  3. ^ Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  321 (English).
  4. ^ A b c John Leslie Jambor , Edward S. Green, Andrew C. Roberts: New Mineral Names. New data . In: American Mineralogist . tape  79 , 1994, pp. 1210–1214 < (English, rruff.info [PDF; 462 kB ; accessed on August 30, 2020]).
  5. ↑ a b c d e Znucalite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 70  kB ; accessed on August 30, 2020]).
  6. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and expanded edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  7. ^ A b David Barthelmy: Znucalite Mineral Data. In: webmineral.com. Accessed August 30, 2020 (English).
  8. ↑ a b c d e f Znucalite. In: mindat.org. Hudson Institute of Mineralogy, accessed August 30, 2020 .
  9. ↑ Ernest H. Nickel , Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed August 30, 2020 .
  10. ↑ a b List of locations for Znucalite from the Mineralienatlas and Mindat , accessed on August 30, 2020.