Hyalophane

Hyalophane, also Bariumfeldspat is a rarely occurring mineral and an intermediate member of the series orthoclase - celsian from the group of the feldspars within the mineral class of " silicate and germanate ". It crystallizes in the monoclinic crystal system with the chemical composition (K, Ba) (Al, Si) 4O8 and usually develops transparent to translucent rhombohedral or prismatic crystals up to 20 cm size, but also granular to massive mineral aggregates.

Special Features

Reiner Hyalophane is colorless. However, it can appear white by multiple refraction due to lattice defects or twinning and accept by foreign admixtures of iron a yellowish or reddish color.

Classification

In the old ( 8th edition ) and new [ [ classification of minerals according to Strunz ( 9th Edition ) # A. Framework silicates ( tectosilicates ) without additional anions | classification of minerals according to Strunz ( 9th Edition )]] is one of the Hyalophane to the Department of framework silicates ( tectosilicates ).

The new, revised Strunz'sche Mineral classification divided here but now more precisely following the absence or presence of zeolitic water of crystallization, and the presence, other anions. According to its composition, which contains no other anions and no water of crystallization than silicon and aluminum, we find the Hyalophane in the subdivision of " framework silicates ( tectosilicates ) without zeolitic H 2 O, without other anions " and there in the feldspar group with the System No.. 9.FA.30 and the other members adularia, anorthoclase, Buddingtonit, celsian, Kokchetavit, microcline, Monalbit, orthoclase, sanidine and Rubiklin.

The commonly used in English-speaking classification of minerals according to Dana assigns the Hyalophane also in the class of silicates, there, however, in the department of " framework silicates with Al- Si lattice ", where he, along with anorthoclase, celsian, Filatovit, microcline, orthoclase Rubiklin and sanidine forms the group of " K (Na, Ba) - feldspars ."

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

Worldwide, Hyalophane so far (as of 2010) are detected at 70 localities, so including 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 ( UK ) and the United States (USA). Also in the Moon Meteorite NWA 773 from Dchira (Western Sahara) Hyalophane was found.

Known for their well-trained, large crystal specimens of up to 15 cm in diameter is especially the " pit Zagradski Potok " in Busovača (Bosnia and Herzegovina).

Crystal structure

Hyalophane crystallizes in the monoclinic space group C2 / m with lattice parameters a = 8.56 Å; b = 13.04 Å; c = 7.20 Å and 115.7 ° β =, and four formula units per unit cell.

Due to its rarity Hyalophane has only among collectors of some value, especially if it has been processed by hobby grinders to gemstones as a mineral specimen.