Hyalophane

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Hyalophane
Hyalophane011.jpg
Hyalophane crystal on host rock from Busovaca, Bosnia
General and classification
chemical formula (K, Ba) (Al, Si) 4 O 8
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.FA.30 ( 8th edition : VIII / J.06)
76.01.01.03
Similar minerals Adular
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 8.56  Å ; b  = 13.04 Å; c  = 7.20 Å
β  = 115.7 °
Formula units Z  = 4
Twinning according to the Carlsbader, Manebacher or Baveno law
Physical Properties
Mohs hardness 6 to 6.5
Density (g / cm 3 ) measured: 2.58 to 2.82; calculated: 2.88
Cleavage perfect after {001}, good after {010}
Break ; Tenacity uneven, mussel-like
colour colorless, white, yellowish, reddish
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.542
n β  = 1.545
n γ  = 1.547
Birefringence δ = 0.005
Optical character biaxial negative

Hyalophane , as Bariumfeldspat known is a rarely occurring mineral and an intermediate member of the series orthoclase  -  celsian from the group of feldspars within the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the chemical composition (K, Ba) (Al, Si) 4 O 8 and is thus chemically seen a potassium - barium silicate, said given in the parentheses elements potassium, barium, aluminum and silicon is each represented in the formula ( substitution , diadochie) can, but always be in the same proportion to the other components of the mineral.

Hyalophane usually develops transparent to translucent, rhombohedral or prismatic crystals up to about 20 cm in size, but also granular to massive mineral aggregates . Pure hyalophane is colorless. However, it can appear white due to multiple refraction due to lattice construction errors or twinning and can take on a yellowish or reddish color due to the addition of iron .

Etymology and history

Hyalophane was first found in 1855 in the “Lengenbach mine” in the Binn valley in the Swiss canton of Valais and described by Wolfgang Sartorius von Waltershausen , who “seem to appear” due to its transparent, glass- shining crystals after the Greek words ὕαλος hyalos “glass” and φαίνειν phainein “Named.

classification

In the old (8th edition) and new systematics of minerals according to Strunz (9th edition) , the hyalophane belongs to the division of tectosilicates.

The new, revised Strunz'sche mineral system, however, now subdivides it more precisely into the absence or presence of zeolitic crystal water and any other anions that may be present . According to its composition, in addition to silicon and aluminum contains no other anions and no water of crystallization, the Hyalophane found in the sub-division of the " framework silicates (tectosilicates) without zeolitic H 2 O, without further anions" and there in the feldspar group with the system -No. 9.FA.30 and the other members Adular , Anorthoklas , Buddingtonit , Celsian , Kokchetavit , Mikroklin , Monalbit , Orthoclase , Rubiklin and Sanidin .

The systematics of minerals according to Dana , which is common in the English-speaking area , also assigns hyalophane to the class of silicates, but there in the department of "framework silicates with Al-Si lattice", where it is used together with Anorthoklas, Celsian, Filatovit , Mikroklin, Orthoclase, Rubiklin and Sanidin form the group of " K (Na, Ba) feldspars ".

Crystal structure

Hyalophane crystallizes monoclinically in the space group C 2 / m with the lattice parameters a  = 8.56  Å ; b  = 13.04 Å; c  = 7.20 Å and β = 115.7 ° and four formula units per unit cell .

Education and Locations

Hyalophane forms either magmatically in phonolite or metamorphically in gneiss , marble and various manganese-containing rocks , but also hydrothermally in veins . Accompanying minerals include analcime , epidote , plagioclase , rhodochrosite , rhodonite , spessartine and tremolite ; in Busovača also apatite , quartz , sagenite and siderite .

So far (as of 2010), hyalophane has been detected at 70 sites around the world, including in Australia , Azerbaijan , Bosnia and Herzegovina , China , Germany , France , Ireland , Israel , Italy , Japan , Canada , Kyrgyzstan , Namibia , New Zealand , Norway , Poland , Sweden , Switzerland , Spain , South Korea , the Czech Republic , the United Kingdom (Great Britain) and the United States (USA). Hyalophane was also found in the lunar meteorite NWA 773 from Dchira (West Sahara ).

The “Zagradski Potok Pit” near Busovača (Bosnia and Herzegovina) is known for its well-developed, large crystal steps of up to 15 cm in diameter .

use

Due to its rarity, hyalophane has a certain value only among collectors as a mineral sample, especially if it has been processed into gemstones by hobby cutters .

See also

literature

Web links

Commons : Hyalophane  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b IMA / CNMNC List of Mineral Names - Hyalophane (English, PDF 1.8 MB; p. 124)
  2. ↑ Webmineral - Hyalophane (English)
  3. ^ A b c 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.  694 .
  4. ↑ a b c Hyalophane , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 76.1 kB )
  5. ↑ a b Hyalophane at mindat.org (engl.)
  6. ↑ Find location list for hyalophane in the Mineralienatlas and Mindat
  7. ^ 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. 242 .