Aphthitalite

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Aphthitalite
Aphthitalite-180031.jpg
Aphthitalite from the salt dome near Qom in Iran
General and classification
other names

formerly Glaserit

chemical formula K 3 Na (SO 4 ) 2
Mineral class
(and possibly department) 		Sulfates (and relatives)
System no. to Strunz
and to Dana 		7.AC.35 ( 8th edition : VI / A.08)
02/28/02/01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral 3 2 / m 1
Room group (no.) P 3 m 1 (No. 164)
Lattice parameters a  = 5.68  Å ; c  = 7.309 Å
Formula units Z  = 1
Twinning repeatedly on {0001} or {11 2 0}
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) 2.66 to 2.71
Cleavage Well
Break ; Tenacity irregular / uneven
colour colorless, white, gray, bluish, greenish, reddish
Line color White
transparency transparent to opaque
shine Glass gloss to resin gloss
Crystal optics
Refractive indices n ω  = 1.487 to 1.491
n ε  = 1.492 to 1.499
Birefringence δ = 0.005
Optical character uniaxial positive
Other properties
Chemical behavior soluble in water, salty and bitter tasting

Aphthitalite (formerly glaserite ) or sulfur potassium salt is a rarely occurring mineral from the mineral class of " sulphates " (and related ones, see classification ). It crystallizes in the trigonal crystal system with the chemical composition K 3 Na [SO 4 ] 2 and develops thin to thick tabular, up to seven centimeters large crystals with a trigonal or by multiple twinning pseudo-orthorhombic habit , but also leafy mineral aggregates or crusty coatings .

Pure aphthitalite is colorless, but it can also appear white due to lattice construction defects or foreign inclusions or it can take on a gray, bluish, greenish or reddish color due to foreign admixtures.

Special properties

The mineral is soluble in water and has a salty to bitter taste.

Etymology and history

Aphthitalite was found for the first time in 1832 on Vesuvius in Italy and described by François Sulpice Beudant , who named the mineral after the Greek words unchangeable and salt in relation to its durability and stability in the air .

Independently of Beudant, Friedrich Hausmann also described the same mineral in 1847 and named it glaserite in honor of the French chemist and pharmacologist Christophe Glaser . This name was later revoked after examination by the CNMNC ( Commission on new Minerals, Nomenclature and Classification , see International Mineralogical Association ), since the right to assign a name lay with the first descriptor Beudant.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the aphthitalite belonged to the mineral class of "sulfates, chromates, molybdates, tungstates" and there to the department of "anhydrous sulfates [SO 4 ], without foreign anions ", where it together with anhydrite , glauberite , kalistrontite and palmierite formed the unnamed group VI / A.08 .

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 aphthitalite to the extended class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)", but also to the Section of “Sulphates (selenates etc.) without additional anions, without H 2 O”. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section "With medium-sized and large cations", where it is the only member of the unnamed group 7.AC.35 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns aphthitalite to the class of "sulfates, chromates and molybdates" and there to the "sulfates" category. Here he is to be found as the only member / together with in the unnamed group 02/28/02 within the subdivision " Anhydrous acids and sulfates with the general formula (A + ) 2 XO 4 ".

Education and Locations

Aphthitalit either forms of fumaroles , where it occurs in the form of crusts or in crystalline form in marine and continental evaporite - or guano - deposits . Depending on the educational conditions, it is then found in paragenesis with various other minerals, including hematite , jarosite , sylvin and thénardite on fumaroles; Blödite , borax , halite , mirabilite , picromerite and syngenite in evaporites; or with syngenite, whitlockite , monetite , nitrocalite and gypsum in guano.

So far (as of 2010) aphthitalite has been detected at almost 40 sites worldwide, including in Australia , China , Germany , France , Iceland , Iran , Italy , Japan , Norway , Austria , Peru , Russia , Saudi Arabia , Ukraine , United States and United Kingdom (Great Britain).

Crystal structure

Aphtitalite crystallizes trigonal in the space group P 3 m 1 (space group no. 164) with the lattice parameters a  = 5.68  Å and c  = 7.309 Å as well as one formula units per unit cell .

See also

Individual evidence

  1. ↑ a b Handbook of Mineralogy - Aphthitalite (English, PDF 62.9 kB)
  2. ↑ a b American Mineralogist Crystal Structure Database - Aphthitalite (English, 1980)
  3. ↑ a b Aphthitalite at mindat.org (engl.)
  4. ^ Mineralienatlas: Glaserit
  5. ↑ Mindat - Localities for Aphthitalite
  6. ↑ American Mineralogist Crystal Structure Database - Aphthitalite (English, 1980)

literature

  • Aphthitalit in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( pdf )

Web links

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