Zektzerite

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Zektzerite
Zektzerite-112541.jpg
Pale pink zectcerite crystals on white albite from Washington Pass, Golden Horn Batholith, Okanogan County, Washington
General and classification
other names

IMA 1976-034

chemical formula NaLiZr [Si 6 O 15 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.DN.05 ( 8th edition : VIII / F.30)
66.03.04.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol rhombic-dipyramidal 2 / m 2 / m 2 / m
Room group (no.) Cmca (No. 64)
Lattice parameters a  = 14.33  Å ; b  = 17.35 Å; c  = 10.16 Å
Formula units Z  = 8
Physical Properties
Mohs hardness ~ 6
Density (g / cm 3 ) measured: 2.79; calculated: 2.8
Cleavage completely according to {100} and {010}
colour colorless to pale pink
Line color White
transparency translucent
shine Glass gloss, pearlescent
Crystal optics
Refractive indices n α  = 1.582
n β  = 1.584
n γ  = 1.584
Birefringence δ = 0.002
Optical character biaxial negative
Other properties
Special features light yellow fluorescence under short-wave UV light

The mineral zektzerite is a very rarely occurring chain silicate from the Tuhualith group. It crystallizes in the orthorhombic crystal system with the chemical composition NaLiZr [Si 6 O 15 ] and develops mostly well-developed crystals with a pseudo-hexagonal, tabular to prismatic habit of white to pale pink with a white line color .

Etymology and history

Zektzerite was first discovered at the "Washington Pass" near Golden Horn in Okanogan County , Washington. First described in 1977 by Pete J. Dunn , Roland C. Rouse , Bart Cannon and Joseph A. Nelen , who named the mineral after Jack Zektzer (* 1936), who made the mineral available to the scientists for their research.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the zektzerite belonged to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where together with pellyite and tuhualith it was an independent group educated.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns zektzerite to the class of "silicates and germanates" and there in the department of "chain and band silicates (inosilicates)" a. This department is, however, further subdivided according to the type of chain formation, so that the mineral, according to its structure, can be found in the subdivision "Chain and band silicates with 6-periodic double chains", where together with Emeleusite and Tuhualith the unnamed group 9.DN .05 forms.

The systematics of minerals according to Dana also assigns zektzerite to the class of "silicates and germanates", but there in the department of "chain silicates: double unbranched chains, W = 2". Here he is together with Tuhualith and Emeleusit in the "Tuhualith group P = 6" with the system no. 66.03.04 can be found in the subsection “ Chain Silicates : Double unbranched chains, W = 2 with chains P> 2 ”.

Education and Locations

Zektzerite forms as a rare crystal filling in " Miarolen ", that is, small cavities within granites or pegmatites , where it is mostly found in paragenesis with aegirine , astrophyllite , elpidite , microcline , quartz , riebeckite or even zircon .

Apart from its type locality "Washington Pass" near Golden Horn in Okanogan County (Washington) in the USA, the mineral could so far (as of 2011) still be found near Darai-Pioz in the Alai Mountains in Tajikistan and near Del Salto in the Chilean province Aisén to be found.

Crystal structure

Zektzerite crystallizes orthorhombically in the space group (space group no. 64) with the lattice parameters a  = 14.33  Å ; b  = 17.35 Å and c  = 10.16 Å and 8 formula units per unit cell .

use

Zektzerite is too rare to be used economically as a raw material or gemstone , and because of its ability to be completely cleaved, it is also too sensitive. Occasionally, however, it is ground into different shapes for collectors .

  • Pink zektzerite in oval facet cut

  • Pear-cut pink zectcerite

See also

Individual evidence

  1. ↑ a b c d e 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. 651 .
  2. ↑ Webmineral - Zektzerite (English)
  3. ↑ a b c Handbook of Mineralogy - Zektzerite (English, PDF 71 kB)
  4. ↑ a b c Zektzerite at mindat.org (engl.)
  5. ^ Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags GmbH, Munich et al. 2002, ISBN 3-405-16332-3 , p. 228 .

literature

Web links

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