Celsian

Celsian is a rarely occurring barium aluminosilicate mineral of the mineral class of silicates and germanates, specifically a tectosilicate ( tectosilicate ) with the chemical composition of Ba [ Al2Si2O8 ]. It crystallizes in the monoclinic crystal system and usually develops massive forms of training, but sometimes short, prismatic to acicular crystals in the centimeter range.

Celsian is a member of the large group of feldspars and forms with orthoclase as the second end member of a mixed batch, their mixed crystals are referred to as Hyalophane.

Etymology and history

The mineral was first found in 1895 and described in the pit Jakob Berg, Nordmark / Värmland in Sweden. It was named after Anders Celsius (1701-1744), a Swedish astronomer, mathematician and physicist.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the celsian belonged to the mineral class of " silicates and Germanates " and then to the Department of " framework silicates ( tectosilicates ) " where he along with Buddingtonit, Hyalophane, Kokchetavit, microcline, orthoclase, Paracelsian, Rubiklin, sanidine and slawsonite the independent " Buddingtonit - orthoclase slawsonite series" formed within the group of the feldspars.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the celsian also in the class of " silicates and Germanates " there but in the meantime finely divided department of the " framework silicates ( tectosilicates ) without zeolitic H2O " one. This department is also further divided according to the possible presence of other anions, so that the mineral is found according to its composition in the subsection " framework silicates ( tectosilicates ) without additional anions ", where it, along with adularia, anorthoclase, Buddingtonit, Hyalophane, Kokchetavit microcline, Monalbit, orthoclase, sanidine Rubiklin and the ' feldspar - group "with the system no. 9.FA.30 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the celsian in the class of " silicates and Germanates " and there in the department of " framework silicates with Al- Si lattice ". Here he is with anorthoclase, Filatovit, Hyalophane, microcline, orthoclase, sanidine Rubiklin and in the group of "K (Na, Ba) - feldspars " with the system no. 76.01.01 found within the subdivision "With Al- Si lattice ".

Modifications and varieties

Another naturally occurring modification of this Bariumalumosilicates is Paracelsian, which likewise monoclinic crystallized, but in a different space group.

On the other hand, the hexagonal modification hexacelsian stable up to the melting point ( > 1700 ° C), only above 1590 ° C and could not have been detected as a natural mineral, however, are probably produced synthetically.

Education and Locations

Celsian formed by regional or contact metamorphism in mn or bariumreichen amphibolites and occurs in paragenesis with barite, known Cymrite, dolomite, hausmannite, Hyalophane, Jakobsit, muscovite, Paracelsian, quartz, rhodochrosite, rhodonite, rutile, Spessartine, Taramellit and zoisite.

Locations in Sweden, in addition to its type locality Nordmark / Värmland still Sundsvall in Medelpad and Nyköping in Södermanland.

Worldwide celsian has been in New South Wales and Tasmania in Australia; Lombardy, Piedmont and Sardinia in Italy; Honshu and Shikoku in Japan; British Columbia, Canada; Almaty in Kazakhstan; Baja California in Mexico; Otjozondjupa in Namibia; eastern Siberia in Russia; and Värmland ( type locality ) in Sweden; Canton of Valais in Switzerland; Moravia in the Czech Republic; in Scotland and Wales in the United Kingdom (Great Britain and Northern Ireland) as well as in Alaska, Arizona, California, Nevada and New Jersey in the United States of America.

Crystal structure

Celsian crystallizes in the monoclinic crystal system in the space group I2 / c with lattice parameters a = 8.62 Å; b = 13.08 Å; c = 14.41 Å and β = 115.1 ° and 8 formula units per unit cell.