Humberstonite

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Humberstonite
General and classification
other names

IMA 1967-015

chemical formula K 3 Na 7 Mg 2 [NO 3 | (SO 4 ) 3 ] 2 · 6H 2 O
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates and tungstates)
System no. to Strunz
and to Dana 		7.DG.10 ( 8th edition : VI / D.16)
02.02.02.01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol trigonal-rhombohedral; 3
Room group (no.) R 3 (No. 148)
Lattice parameters a  = 10.90  Å ; c  = 24.40 Å
Formula units Z  = 3
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) measured: 2.252; calculated: 2.252
Cleavage completely after {0001}
Break ; Tenacity irregular
colour colorless to white
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.474
n ε  = 1.436
Birefringence δ = 0.038
Optical character uniaxial negative
Other properties
Chemical behavior water soluble

Humberstonite is a very rarely occurring mineral from the mineral class of the " sulfates " (and relatives, see classification ). It crystallizes in the trigonal crystal system with the chemical composition K 3 Na 7 Mg 2 [NO 3 | (SO 4 ) 3 ] 2 · 6H 2 O, so it is chemically a water-containing potassium - sodium - magnesium - nitrate sulphate .

Humberstonite is mostly found in the form of massive mineral aggregates , but also forms hexagonal, tabular crystals up to about 0.3 millimeters in size. In its pure form, humberstonite is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or polycrystalline formation, it can also appear white, with the transparency decreasing accordingly.

Special properties

Humberstonite is soluble in water.

Etymology and history

Humberstonite was first discovered on the mining site "Oficina Alemania" near Santa Catalina (Antofagasta) in the Chilean Región de Antofagasta and described in 1967 by George E. Ericksen, Joseph J. Fahey, Mary E. Mrose, who named the mineral in honor of the chemist James Thomas Humberstone (1850-1939) named. Its scientific contributions enabled a more cost-effective mining of nitrates from the Chilean deposits.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the humberstonite belonged to the class of "sulfates, chromates, molybdates and tungstates" and there to the general department of " hydrous sulfates with foreign anions ", where together with carloruizite , Fuenzalidait , Georgeericksenit , Darapskit , Klinoungemachit and Ungemachit formed the unnamed group VI / D.16 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns humberstonite to the extended class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)", but also to the Department of "Sulphates (selenates etc.) with additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved and the predominant anion complexes in the compound, so that the mineral is classified according to its composition in the sub-section “With large to medium-sized cations; with NO 3 , CO 3 , B (OH) 4 , SiO 4 or IO 3 “, where it forms the unnamed group 7.DG.10 together with Klinoungemachite and Ungemachit .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the humberstonite to the class of "sulfates, chromates and molybdates" and there to the department of "composite sulfates". Here he is to be found as the only member of the unnamed group 32.02.02 within the subdivision of “ Compound sulfates (containing water) with a simple double anionic formula ”.

Education and Locations

Humberstonite is formed by repeated, natural leaching of nitrate ores with reprecipitation in ore lenses above the local regolith deposits . The accompanying minerals include blödit , nitronatrite and kieserite .

Apart from its type locality Oficina Alemania, the mineral has only been found in Chile in the "Pedro de Valdivia" mine near Pedro de Valdivia in the province of Tocopilla (Región de Antofagasta). It was also found at the salt lakes of Qakilik ( Ruoqiang ) and in the Tarim river valley in the Mongolian Autonomous District of Bayingolin in China.

Crystal structure

Humberstonite crystallizes trigonally in the space group R 3 (space group no. 148) with the lattice parameters a  = 10.90  Å and c  = 24.40 Å and 3 formula units per unit cell .

See also

literature

  • George E. Ericksen, Joseph J. Fahey, Mary E. Mrose: Humberstonite, Na 7 K 3 Mg 2 (SO 4 ) 6 (NO 3 ) 2 6H 2 O: A new saline mineral from the Atacama Desert, Chile , in : Geological Society of America , Abstracts Annual Meetings 1967, pp. 59–59 ( PDF 65.8 kB )
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 671 .
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 617 (first edition: 1891).

Web links

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  410 .
  2. ↑ Webmineral - Humberstonite
  3. ↑ a b Humberstonite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.9 kB )
  4. ↑ a b c Mindat - Humberstonite