Glaucophane
Glaucophane is a rarely occurring mineral from the mineral class of silicates and Germanates. It crystallizes in the monoclinic crystal system with the chemical composition □ Na2 (Mg, Fe) 3Al2 [( OH) 2 | Si8O22 ]. The values given in the parentheses of the elements magnesium and iron can relax in the formula each represent each other (substitution, Diadochie ), but are always in the same proportions to the other components of the mineral. The symbol □ indicates that this space is not completely filled structure.
Glaucophane is translucent and developed prismatic crystals, but usually occurs in columnar, fibrous, granular or massive mineral aggregates. Its color varies from black to blue, gray-blue and lavender; It may also have a color change zonaren. On the dash panel glaucophane leaves a blue-gray line. In unweathered crystal faces shows a glass-like shine.
Etymology and history
The mineral was named because of its distinctive bluish- gray color after the ancient Greek words Γλαύκος Glaucus for sparkly, shiny, bright, the bright shine of the sky, the sea, or of the human eye is meant and in terms of the color leaves a certain margin, and φαίνω Phaino for " seem to appear ".
Was first found and described in 1845 by Johann Friedrich Ludwig glaucophane Hausmann. As a type locality applies the Greek island of Syros.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the glaucophane belonged to the department of " chain silicates and phyllosilicates ( inosilicates ) " where he along with Arfvedsonite, Dellaventurait, Eckermannit, Ferrinybøit, ferric Ottoliniit, Ferriwhittackerit, Ferro - Eckermannit, Ferroglaukophan, Ferroleakeit, fluoro- Ferroleakeit, fluoro- potassium magnesio - Arfvedsonite, fluoro - magnesio - Arfvedsonite, fluoro- Natriumpedrizit, Fluoronybøit, Kaliumarfvedsonit, Kaliumleakeit, Kornit, Kozulith, Leakeit, magnesio - Arfvedsonite, Magnesioriebeckite, sodium Ferripedrizit, sodium ferric Ferropedrizit, Nybøit, Obertiit, riebeckite and Ungarettiit the subgroup of " alkali amphiboles " with the system no. VIII/F.08 formed within the amphibole group.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the glaucophane also included in the department's " chain and chain silicates ( inosilicates ) ". This division, however, is further subdivided according to the crystal structure and membership of closely related mineral families, so that the mineral as a member of the " alkali - Klinoamphibole, glaucophane Eckermannit group " with the system no. Is to find 9.DE.25.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the glaucophane in the department of " chain silicates: Double unbranched chains, W = 2". Here he belongs to " group 4, sodium amphiboles " with the system no. 66.01.03c within the subdivision " chain silicates: Double unbranched chains, W = 2 amphibole configuration ".
Modifications and varieties
- Gastaldit is a solid solution between glaucophane and actinolite, in which predominates the Aktinolithanteil.
- Crossite (1997 discredited by the IMA ) is considered as one member of the series and Ferroglaukophan glaucophane or riebeckite series or Magnesioriebeckite.
Education and Locations
Glaucophane forms as typical metamorphic mineral mainly in schists and gneisses. Accompanying minerals occur among others actinolite, aragonite, Barroisite, chlorite, crossite, cummingtonite, epidote, jadeite, lawsonite, omphacite and pumpellyite.
As a rather rare mineral formation glaucophane may indeed be abundant in part to different sites, overall it is not very common. So far (as of 2012) are considered to be known around 230 localities. Apart from its type locality, the mineral Syros still occurred in Greece on other islands of the Cyclades and at Neapolis Vion ( Neapolis ) in Laconia, at Arki in the southern Aegean and Evia in central Greece.
In Austria, the glaucophane at several locations in Carinthia ( Hohe Tauern, Villach ) and Salzburg ( grave Bach) could be found. The only known locality in Germany Triberg in the Black Forest and the mineral was found in Switzerland in a few places in the municipality in the canton of Valais Tasch.
Other localities lie among other things in Antarctica, Australia, China, Ecuador, France, Guatemala, Italy, Jamaica, Japan, Columbia, Cuba, Madagascar, Macedonia, Myanmar, New Caledonia, Norway, Oman, Portugal, Romania, Russia, Sweden, Slovakia, Czech Republic, Turkey and the United States of America.
Crystal structure
Glaucophane crystallizes in the monoclinic crystal system, space group C2 / m with lattice parameters a = 9.53 Å, b = 17.74 Å and c = 5.30 Å; β = 103.7 ° and two formula units per unit cell.