Barrerite

Barrerit is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition Na2 [ Al2Si7O18 ] · 6 H2O and is found predominantly in the form of transparent to translucent, tafeliger crystals up to 5 cm in size.

Special Features

Reiner Barrerit is colorless. By lattice defects or foreign admixtures he shows up, however, usually in white, reddish white or pink color.

Etymology and history

Was first found in 1974 on the Barrerit andesite rocks at San Efisio ( Nora ) in the province of Cagliari and described by E. Passaglia and D. Pongiluppi that the minerals by Richard Maling Barrer ( 1910-1996 ), a New Zealand chemist and founder zeolite chemistry, named.

Classification

In the now outdated but still in use classification of minerals according to Strunz ( 8th edition ) of the Barrerit belonged to the department of " framework silicates ( tectosilicates ) " and there to the zeolite group (subgroup Blätterzeolithe ).

The revision of the Strunz'schen Mineral classification in its 9th edition, this department was precisely divided according to the type of binding form of scaffolding. Accordingly, the Barrerit now in the subdivision of " framework silicates ( tectosilicates ) with zeolitischem H2O; To find family of zeolites and panels with 4-4-1-1 structural units ".

The commonly used in English-speaking classification of minerals according to Dana assigns the Barrerit also in the department of " framework silicates: Zeolite Group " and then in the group of " heulandites and related species ".

Education and Locations

The exact formation conditions of Barrerit date, nothing is known. He finds, however, mainly on the walls of large fractures strongly weathered andesite and rhyolite lava or other alkaline - igneous rocks, such as diabase (USA), where he appears among others in paragenesis with heulandite.

Apart from its type locality San Efisio Barrerit was found in Italy nor in Pula in Sardinia. Overall, the mineral has been able (as of 2010 ) can be detected at eleven localities: In the " Cantung Mine" with Tungsten ( Northwest Territories ) and in the " Woodworth Cove " ( Woodworth cave ) on the Bay of Fundy in Canada; at Hirado in Japan; in the Norwegian municipality Vefsn and on Kuiu Iceland (Sitka Borough, Alaska), in Pershing County ( Nevada ) and at Cedar Mountain in Mitchell ( Culpeper County, Virginia) in the USA.

Crystal structure

Barrerit crystallizes in the orthorhombic space group Amma with the lattice parameters a = 13.64 Å, b = 18.20 Å and c = 17.84 Å, and eight formula units per unit cell.