Aenigmatite
The mineral Aenigmatit is a rarely occurring chain silicate from the mineral class of silicates. It crystallizes in the triclinic crystal system with the chemical composition Na2 ( Fe2 4 Ti) Fe2 [ O2 | Si6O18 ] and usually develops short prismatic crystals of black color with red-brown stroke color. Thin fins are brownish translucent.
With Wilkinsonit Aenigmatit forms a mixed batch.
Etymology and history
Was first described Aenigmatit and its type locality, the Ilímaussaq intrusion in the vicinity of Kangerdluarssuq Fjord in southwest Greenland, 1865 by August Breithaupt ( 1791-1873 ), who named the mineral after the Greek word αἴνιγμα ( " the riddle " ) in order declare its originally unexplained chemical composition.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Aenigmatit belonged to the mineral class of " silicates and Germanates " and then to the Department of " chain silicates and phyllosilicates ( inosilicates ) " where he, along with Dorrit, Høgtuvait, Krinovit Manganilvait, Makarochkinit, Rhönit, Serendibite, Welshit and Wilkinsonit " Aenigmatit group" was formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Aenigmatit also in the class of " silicates and Germanates " and there in the department of " chains and chain silicates ( inosilicates ) " one. This division, however, is further subdivided by the structure of the chains so that the mineral is found according to its crystal structure in the subdivision " chain and chain silicates with 4- periodic single chains, Si4O12 " where there along with Baykovit, Dorrit, Høgtuvait, Krinovit, Makarochkinit, Rhönit, Serendibite, Welshit and Wilkinsonit forms the unnamed group 9.DH.40.
The classification of minerals according to Dana assigns the Aenigmatit in the class of " silicates and Germanates " there, however in the department of " chain silicates: chains with side branches or loops " one. Here he is as a name the group " Aenigmatit and related species ( Aenigmatit subgroup ) " with the system no. Within the subdivision 69.02.01a and the other members Dorrit, Høgtuvait, Krinovit, Rhönit, Serendibite, Welshit, Wilkinsonit and Makarochkinit " chain silicates: > 2 chains with side branches or loops with P" to find.
Education and Locations
Aenigmatit forms usually in bright, sodium - stressed ( alkaline ) magma rocks. Among them would be to call:
- Sodium syenites and trachytes sodium
- Pantellerite and Commendite
- Nepheline syenites ( Foyaite )
- Phonolites and
- Nepheline syenite pegmatites.
Is associated Aenigmatit especially with aegirine, riebeckite and Arfvedsonite, but also albite, anorthoclase, Astrophyllite, augite, fayalite, hedenbergite, ilmenite and you may also have.
Worldwide, Aenigmatit so far (as of 2011) to nearly 100 localities. Apart from its type locality Ilímaussaq the mineral in Greenland nor in Igaliku, Nunarssuit and Quagdlimiut the district Kitaa and in Kangerlussuaq and the Kialineq Bay took place in the district tunu.
Other localities are Tasmania in Australia, the northern and southwestern regions of Cameroon, several regions of Canada, Mianning in China, Pantelleria in Italy, the Japanese island of Honshu, the Ampasindava Peninsula of Madagascar, the Mongolian Altai Mountains, at Aris in the Namibian region Khomas, New Zealand, the Nigerian region of Agadez, Kangwŏn -do in North Korea, several regions of the Norwegian provinces Telemark and Vestfold, the Azores in Portugal, several regions of the Russian Kola Peninsula, which belongs to St. Helena, Ascension and Tristan da Cunha Ascension Island, Gyeongsangbuk-do South Korea, South Yemen, the Ngorongoro crater in Tanzania, Strathclyde, United Kingdom, Ukraine Mecsek Hungary and several regions in the United States.
Crystal structure
Aenigmatit crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 2) with the lattice parameters a = 10.41 Å; b = 10.81 Å; c = 8.93 Å; α = 104.9 °; β = 96.9 ° and γ = 125.3 ° and two formula units per unit cell.