Stronalsite

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Stronalsite
General and classification
other names

IMA 1983-016

chemical formula SrNa 2 [Al 4 Si 4 O 16 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.FA.60 ( 8th edition : VIII / J.07)
76.01.06.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal mm 2
Space group Ibam
Lattice parameters a  = 8.42  Å ; b  = 9.90 Å; c  = 16.73 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 6.5
Density (g / cm 3 ) 2.95
Cleavage Please complete!
colour colorless, white
Line color White
transparency translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.563
n β  = 1.564
n γ  = 1.574
Birefringence δ = 0.011
Optical character biaxial positive
Axis angle 2V = measured: 32 °; calculated: 36 °

Stronalsite is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition of sRNA 2 [Al 4 Si 4 O 16 ], and thus forms the strontium analogue of Banalsits (BANA 2 [Al 4 Si 4 O 16 ]).

Stronalsite develops white, translucent (also colorless in thin layers), short prismatic crystals up to about a millimeter in length, which often form block-shaped aggregates.

Etymology and history

The name Stronalsit is an acronym , formed from the main components of the chemical elements involved in the compound strontium (Sr), sodium (Na), aluminum (Al) and silicon (Si).

The mineral was first discovered in 1983 in the "Tanaka quarry" near Kōchi in Japan and described by Hidemichi Hori, Izumi Nakai, Kozo Nagashima, Satoshi Matsubara and Akira Kato. It was recognized as an independent mineral by the International Mineralogical Association (IMA) in the year of its discovery under the internal accession number IMA 1983-016 .

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of banalsite belonged to the mineral class of "silicates and Germanates" and there to the general ward of the " framework silicates (tectosilicates)" where he eponymous member of anorthoclase anorthite Banalsit- Series with the other members albite , andesine , anorthite , anorthoclase , banalsite , bytownite , dmisteinbergite , filatovite , labradorite , oligoclase and svyatoslavite is within the large group of feldspars .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns stronalsite to the class of "silicates and germanates", but in the new section of "tectosilicates without zeolite H 2 O" a. This section is further subdivided according to the presence of further anions in the chemical formula, so that the mineral, according to its composition, can be found in the sub-section "Tectosilicates (tectosilicates) without additional anions", where it only belongs to group 9 together with banalsite .FA.60 forms.

The systematics of minerals according to Dana also assigns the stronalsite to the class of "silicates and germanates" and there in the department of "framework silicates with Al-Si lattice". Here he is together with Banalsit, Lisetit and Svyatoslavit in the "Banalsitgruppe" named after him with the system no. 76.01.06 to be found in the subsection " With Al-Si grid ".

Education and Locations

Stronalsite forms in the form of small veins in xenolites of ultra-basic tuffs . Accompanying minerals include slavsonite and pectolite .

In addition to its type locality in the "Tanaka quarry" on Shikoku , the mineral could also be found in Japan at Itoigawa and at Ohsa ( Okayama ) on Honshū . Stronalsite was also found in the Zhidoiskii massif of Irkutsk Oblast and the Chibinen on the Kola peninsula in Russia and in the Pilansberg complex near Rustenburg in South Africa. A site on Fuerteventura in Spain is not certain .

Crystal structure

Stronalsite crystallizes orthorhombically in the space group Ibam with the lattice parameters a  = 8.42  Å ; b  = 9.90 Å and c  = 16.73 Å as well as 4 formula units per unit cell .

See also

Web links

literature

  • Hidemichi Hori, Izumi Nakai, Kozo Nagashima, Satoshi Matsubara, Akira Kato: Stronalsite, SrNa 2 Al 4 Si 4 O 16 , a new mineral from Rendai, Kochi City, Japan . In: Mineralogical Journal . tape 13 , no. 6 , 1986, pp. 368–375 , doi : 10.2465 / minerj.13.368 (free full text).

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. 697 .
  2. ↑ Webmineral - Banalsite (English)
  3. ↑ a b c d Stronalsite at mindat.org (engl.)