Barrerite

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Barrerite
Barrerite-91257.jpg
Barrerite from Rocky Pass, Kuiu Island , Alaska, USA (size: 9 × 4 cm)
General and classification
chemical formula Na 2 [Al 2 Si 7 O 18 ] • 6 H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.GE.15 ( 8th edition : VIII / J.23)
01/07/07/05
Similar minerals Stilbit , stellerite
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal 2 / m 2 / m 2 / m
Space group Amma
Lattice parameters a  = 13.64  Å ; b  = 18.20 Å; c  = 17.84 Å
Formula units Z  = 8
Frequent crystal faces {010}, {001}, {100}, {011} and {111}
Physical Properties
Mohs hardness 3 to 4
Density (g / cm 3 ) 2.13 (measured); 2.11 (calculated)
Cleavage completely after {010}
colour colorless, white, reddish white, pink
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.479
n β  = 1.485
n γ  = 1.489
Birefringence δ = 0.010
Optical character biaxial negative
Axis angle 2V = 78 °
Other properties
Chemical behavior sparingly soluble in hydrochloric acid

Barrerite is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition Na 2 [Al 2 Si 7 O 18 ] · 6 H 2 O and is mainly found in the form of transparent to translucent, tabular crystals with a size of up to 5 cm.

Etymology and history

Barrerite was first found in 1974 on the andesite rock near San Efisio (Nora) in the Italian province of Cagliari and described by E. Passaglia and D. Pongiluppi, who named the mineral after Richard Maling Barrer (1910-1996), a New Zealand chemist and founder of zeolite chemistry.

classification

In the meanwhile outdated, but still common systematics of minerals according to Strunz (8th edition) , the barrerite belonged to the department of " framework silicates (tectosilicates)" and there to the zeolite group (subgroup leaf zeolites).

With the revision of Strunz's mineral system in the 9th edition , this section was subdivided more precisely according to the type of binding form of the framework. Accordingly, the Barrerit now in the sub-division of the " framework silicates (tectosilicates) with zeolitischem H 2 O; Family of zeolites and sheets with 4-4-1-1 structural units ”.

The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns the barrerite to the department of “framework silicates: zeolite group” and there to the group of “ heulandites and related species ”.

Crystal structure

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

properties

Pure barrerite is colorless. However, due to lattice construction errors or foreign admixtures, it usually shows itself in white, reddish-white or pink color.

Education and Locations

Tabular barrerite (left) and 7 cm long “sugar quartz” stalactite (right) from Rocky Pass, Kuiu Island

So far nothing is known about the exact educational conditions of Barrerit. However, he finds himself mainly on the walls of large fractures strongly weathered andesite and rhyolite - lava or other alkaline-igneous rocks, such as diabase (USA), where he, among others, in paragenesis with Heulandit occurs.

In addition to its type locality San Efisio, Barrerit was found in Italy near Pula on Sardinia. In total, the mineral has so far (as of 2010) been found at eleven locations: In the "Cantung Mine" near Tungsten (Northwest Territories) and in "Woodworth Cove" ( Woodworth Cave ) on the Bay of Fundy in Canada; at Hirado in Japan; in the Norwegian municipality of Vefsn and on Kuiu Island ( Sitka Borough, Alaska), in Pershing County (Nevada) and on Cedar Mountain near Mitchell ( Culpeper County , Virginia) in the USA.

See also

Individual evidence

  1. ↑ Webmineral - Barrerite (English)
  2. ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 708 .
  3. ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  4. ↑ Handbook of Mineralogy - Barrerite (English, PDF 76.2 kB)
  5. ↑ a b c Barrerite at mindat.org (engl.)
  6. ↑ Mindat - picture example of a colorless barrery
  7. ↑ Mindat - Localities for Barrerite

literature

Web links

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