Hardship

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Hardship
General and classification
chemical formula K 3 Na 8 Fe 3+ [(NO 3 ) 2 | (SO 4 ) 6 ] • 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)
02.02.03.01
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  = 24.99 Å
Formula units Z  = 3
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) measured: 2.287 (3); calculated: [2,259]
Cleavage completely after {0001}
Break ; Tenacity uneven; brittle
colour colorless, light yellow
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.502
n ε  = 1.449 (2)
Birefringence δ = 0.053
Optical character uniaxial negative
Other properties
Chemical behavior soluble in weak hydrochloric acid

Ungemachite is a very rarely occurring mineral from the mineral class of " sulfates " (and relatives, see classification ). It crystallizes in the trigonal crystal system with the composition K 3 Na 8 Fe 3+ [(NO 3 ) 2 | (SO 4 ) 6 ] · 6H 2 O, so chemically speaking it is a water-containing potassium - sodium - iron - nitrate sulfate.

Ungemachit only develops small crystals up to about one millimeter in size with a tabular habit . In its pure form it is colorless and transparent with a glass-like sheen on the surfaces. However, due to multiple refraction due to lattice construction defects or polycrystalline design, it can also appear white and, due to foreign admixtures, take on a light yellow color, the transparency decreasing accordingly.

Special properties

Ungemachit is already soluble in weak hydrochloric acid.

Etymology and history

Was first discovered in 1935 in the Ungemachit porphyry copper - deposit at Chuquicamata in northern Chile. It was described in 1936 by Martin Alfred Peacock and Mark Chance Bandy , who named the mineral after the Belgian crystallographer Henri Léon Ungemach (1879–1936) in order to honor his studies on the natural sulphates of Chile.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the ungemachite belonged to the class of "sulfates, chromates, molybdates and wolframates" and there to the general section of " hydrous sulfates with foreign anions ", where together with carloruizite , Darapskite , Fuenzalidaite , Georgeericksenite , Humberstonite and Klinoungemachite formed the unnamed group VI / D.16 .

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), assigns the ungemachite 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 clinoungemachite and humberstonite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the ungemachite to the class of "sulfates, chromates and molybdates" and there in the section of "composite sulfates". Here he is to be found as the only member of the unnamed group 02.02.03 within the subdivision of " Compound sulfates (containing water) with a simple double-anionic formula ".

Education and Locations

Ungemachit is formed by the oxidation of pyrite under arid climatic conditions and is found as crack or cavity fillings in other massive iron sulphates. As Begleitminerale occur among other Fibroferrit , jarosite , Klinoungemachit, Metasideronatrit , Metavoltin and Sideronatrite on.

So far (as of 2012), apart from its type locality Chuquicamata in Chile , the mineral could only be detected in the "New Cobar" mine near the city of the same name in Cobar in the Australian state of New South Wales.

Crystal structure

Ungemachit crystallizes trigonally in the space group R 3 (space group no. 148) with the lattice parameters a  = 10.90  Å and c  = 24.99 Å as well as 3 formula units per unit cell .

See also

literature

  • MA Peacock, MC Bandy: Ungemachite and Clino-Ungemachite: New Minerals from Chile , in: American Mineralogist , Volume 23 (No. 5, 1938), pp. 314–328 ( PDF )

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 - Ungemachite
  3. ↑ a b c Ungemachite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.6 kB )
  4. ↑ a b c Mindat - Ungemachite
  5. ↑ MA Peacock, MC Bandy: Ungemachite and Clino-Ungemachite: New Minerals from Chile (see literature)