Carobbiite

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Carobbiite
General and classification
other names

Potassium fluoride

chemical formula Theatrical Version
Mineral class
(and possibly department) 		Halides
System no. to Strunz
and to Dana 		3.AA.20 ( 8th edition : III / A.02)
01/09/01/04
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fm 3 m (No. 225)Template: room group / 225
Lattice parameters a  = 5.34  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 2 to 2.5
Density (g / cm 3 ) measured: not defined; calculated: [2.53]
Cleavage good after {001}
colour colorless
Line color White
transparency translucent
shine Glass gloss
radioactivity weak radioactivity (potassium 40)
Crystal optics
Refractive index n  = 1.362
Other properties
Chemical behavior well soluble in water
Special features poisonous mineral

Carobbiite is a very seldom occurring mineral from the mineral class of halides with the chemical composition KF and thus, from a chemical point of view, potassium fluoride .

Carobbiite crystallizes in the cubic crystal system and usually develops tiny, colorless to white, cubic crystals .

Etymology and history

Naturally occurring potassium fluoride was first found and described by the Italian geologist Guido Carobbi on Vesuvius in Italy in 1936 . However, it was not recognized as a mineral until 1956, when Hugo Strunz re-examined the material and confirmed Carobbi's discoveries. He named the mineral after its original discoverer.

classification

Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the carobbiite belonged to the mineral class of "halides" and there to the section "simple halides", where together with bromargyrite , chlorargyrite , halite , sylvite and villiaumite it forms the "halite Series "with the system no. III / A.02 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies carobbiite in the somewhat more refined section “Simple halides without H 2 O”. This is further subdivided according to the molar ratio of metal (M) to halogen (X), so that the mineral can be found according to its composition in the sub-section "M: X = 1: 1 and 2: 3", where it can be found together with Griceit , Halit, Sylvin and Villiaumit the "Halitgruppe" with the system no. 3.AA.20 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the carobbiite to the class and division of the same name of "halides". Here he is also a member of the "Halitgruppe" with the system no. 01/09/01 to be found in the subsection " Anhydrous and hydrous halides with the formula AX ".

Crystal structure

Structure of carobbit

Carobbiite crystallizes in the cubic crystal system in the space group Fm 3 m (space group no. 225) with the lattice parameter a = 5.34  Å and four formula units per unit cell . Template: room group / 225

properties

Due to its potassium content of up to 67.30% with a proportion of radioactive 40 K of a maximum of 0.0117%, carobbiite can be weakly radioactive. Taking into account the proportions of the radioactive elements in the idealized empirical formula and the subsequent decays of the natural decay series, a specific activity of about 20 Bq / g is given for the mineral  . 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

Carobbiite forms in stalactites in lava caves . It is associated with halite, mercallite and hieratite . In addition to the type locality on Vesuvius, only one other site is known in Iburi prefecture on the Japanese island of Hokkaidō .

See also

literature

  • Hugo Strunz: Carobbiite, a new mineral . In: Rendiconti della Società Mineralogica Italiana . tape 12 , 1956, pp. 212-213 .
  • Michael Fleischer: New Mineral names . In: American Mineralogist . tape 42 , no. 1-2 , 1957, pp. 117 (English, minsocam.org [PDF; 464 kB ; accessed on November 27, 2018]).

Web links

Individual evidence

  1. ^ A b c 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.  150 (English).
  2. ↑ Mindat Carobbiit - Carobbiite (English)
  3. ↑ a b Carobbiite . 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]).
  4. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  5. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 376 .
  6. ↑ a b Michael Fleischer: New Mineral names . In: American Mineralogist . tape 42 , no. 1-2 , 1957, pp. 117 (English, minsocam.org [PDF; 464 kB ; accessed on November 27, 2018]).
  7. ↑ Webmineral - Carobbiite (English)
  8. ↑ Find location list for carobbiite in the Mineralienatlas and in Mindat