Alunite

• Alum
• Alaunspat
• Lœvigit
• Lœwigit

Alunite and alunite, Alaunspat, Lœvigit or Lœwigit, is a rarely occurring mineral from the mineral class IV ( sulfates, selenates, tellurates, chromates, molybdates, tungstates ), or more precisely a basic, anhydrous potassium aluminum sulfate. It crystallizes in the trigonal crystal system, with the chemical composition KAl3 [( OH) 6 | (SO4) 2]. Alunite developed either flattened cube-shaped, rhombohedral crystals or porous granular aggregates of white -yellow to reddish color.

Special Features

Alunite is a pyroelectric and piezoelectric crystal, which also still fluoresces orange when illuminated with ultraviolet light.

Etymology and history

Alunite derived from alum (from the Latin alumen ), was first mined in the 15th century in Tolfa near Rome for the alum - production under the control of the Popes. 1707 was described by Jean -Claude Delamétherie as Aluminilit what was then shortened in 1824 by François Sulpice Beudant to alunite. Albrecht Dürer made ​​a alunite crystal dar. on his engraving Melencolia I ( 1514)

Classification

Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of alunite for mineral class of " sulfates ( and Related ) " and then to the Department of " water clear sulfates, with foreign anions ", where he was named the " alunite group "with the system no. Formed VI/B.11 and the other members Ammonioalunit, Ammoniojarosit, Argentojarosit, Beaverite, Dorallcharit, Huangit, hydronium jarosite, jarosite, Krivovichevit, Minamiit, natroalunite, Natrojarosite, Osarizawait, plumbojarosite and Walthierit.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the alunite also in the department of " sulfates ( selenates, etc.) with additional anions, without H2O" one. However, this is further divided according to the relative size of the cations involved, so that the mineral is found according to its composition in the subsection "With medium -sized and large cations " where there is also eponymous the " alunite - group " with the system no. Forms 7.BC.10 and the other members Ammonioalunit, Ammoniojarosit, Argentojarosit, Beaverite, Dorallcharit, Huangit, hydronium jarosite, jarosite, Minamiit, natroalunite, Natrojarosite, Osarizawait, plumbojarosite, Schlossmacherit and Walthierit.

The mainly common in English-speaking classification of minerals according to Dana assigns to the category of " sulfates, chromates and molybdates " and there in the department of " water clear sulfates with hydroxyl or halogen" one. Here he is in the " Alunitgruppe ( alunite subgroup ) " with the system no. 30.02.04 " by hydroxyl or halogen with (AB) 2XO4Zq Anhydrous sulfates " found within the subdivision.

Education and Locations

Rarely do you find well-trained single crystals in geodes. Alunite crystallizes in a hexagonal system to trigonal pyramids, which are often fused into multiple crystals. Chemically, the mineral is a basic potassium aluminum sulfate. If sodium in the place of potassium, it is called soda- alunite, the aluminum is replaced by iron (Fe3 ) of jarosite. The latter occurs in particular when the secondary mineral in iron sulfate-containing ores. The mineral is insoluble in water and weak acids, but readily soluble in sulphurous acid.

Was alunite so far (as of 2009) detected at about 700 localities, so among other things in Egypt, Argentina, Australia, Bolivia, Brazil, Bulgaria, Chile, China, Costa Rica, Germany, Dominican Republic, Ecuador, Eritrea, Fiji, France, Greece, England in Great Britain, India, Indonesia, Iran, Italy, Japan, Virgin Islands, Canada, Kazakhstan, Kyrgyzstan, Colombia, Madagascar, Morocco, Macedonia, Mexico, Mongolia, Myanmar, New Zealand, Austria, Papua New Guinea, Peru, Philippines, Poland, Romania, Russia, Solomon Islands, Serbia, Slovakia, Spain, South Africa, South Korea, Taiwan, Turkey, Turkmenistan, Ukraine, United States.

Crystal structure

Alunite crystallizes in the trigonal crystal system in the space group R3m with lattice parameters a = 6.9741 Å and c = 17.190 Å and four formula units per unit cell.

Use

The raw material

Alunite is now mined as potassium and aluminum ore. Larger deposits are located in Tuscany and Hungary, as well as in New South Wales, Colorado, Nevada, Utah, and in the Red Mountains in Arizona.

Medical importance

The alum is an antiseptic ( pathogen -inhibiting and inactivating ) and astringent ( astringent, sealing ). It is used as a hemostatic pin to close small wounds that occur frequently while shaving. In the wet shave he serves as an aftershave, in the electric shave as preshave.

Body Care

Alum is an effective and cheap deodorant, free of chemical additives ( irritants, preservatives ) and therefore well tolerated. Lightly wet out on the skin, it binds the odor -producing molecules reliably (see also Deokristall ).

Speleology ( caving )

Alunite is an aid in determining the age of caves, as it is reflected on the walls of the forming cavity when offset with sulfuric acid groundwater penetrates the limestone.

Gem

Recently, alunite is re-used as a gemstone (mainly cabochon ). In the Austrian Waldviertel found alunite is also referred to as " Bernhardit " ( after the archaeological site of Bernard ).