Pachnolite
| Pachnolite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | CaNaAlF 6 · H 2 O |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.CB.40 ( 8th edition : III / C.02) 06/11/05/01 |
| Similar minerals | Thomsenolite , Yaroslavite |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | 2 / m |
| Space group | F 2 1 / d |
| Lattice parameters |
a = 12.117 Å ; b = 10.414 Å; c = 15.680 Å β = 90.37 ° |
| Formula units | Z = 16 |
| Twinning | along {100} |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | 2.98 |
| Cleavage | hardly recognizable |
| Break ; Tenacity | shell-like |
| colour | colorless, white, brownish due to limonite |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices | n α n α = 1.4065; n β = 1.4104; n γ = 1.4191 |
| Axis angle | 2V = 66.9 to 76 ° |
Pachnolite , also known as pyroconite , is a rare mineral from the mineral class of halides . It crystallizes in the monoclinic crystal system with the chemical composition CaNaAlF 6 · H 2 O and forms elongated, prismatic, colorless or white crystals up to eight centimeters in size along [001].
Etymology and history
The mineral was first in 1863 by Adolph Knop in one of Greenland derived cryolite discovered -Erz and described. He named it after the Greek πάχνη for ripe , as the pachnolite formed a ripe- like crust on cryolite.
classification
In the meantime outdated classification of minerals by Strunz (8th edition) of Pachnolith still belongs to the department of "hydrous Doppelhalogenide" without further subdivisions, where he together with Tomsenolith and Yaroslavit the unnamed group III / C.02 forms.
Since the 2001 restructuring and partial redefinition of the classes in the 9th edition of Strunz's mineral systematics, the mineral can be found in the new section of "Complex Halides" and there in the sub-section of "Island aluminofluorides (Neso-aluminofluorides)" where it only forms the unnamed group 3.CB.40 together with thomsenolite .
The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns the pachnolite to the class of halides, but there in the department of “ Complex halides - aluminum fluorides with various formulas ”, where the mineral is the only member of the unnamed group 11.06.05 .
Crystal structure
Pachnolite crystallizes monoclinically in the space group F 2 1 / d with the lattice parameters a = 12.117 Å ; b = 10.414 Å; c = 15.680 Å and β = 90.37 ° and 16 formula units per unit cell .
properties
Pachnolite dissolves well in sulfuric acid , forming the toxic hydrogen fluoride .
morphology
Pachnolite crystals are prismatic and elongated along {001}. They are angular with sharp edges and taper to a point. The crystals are striped parallel to {001}.
Modifications and varieties
Pachnolite is dimorphic to Thomsenolite.
Education and Locations
Pachnolite is secondary to aging from cryolite or other aluminum fluorides. It is usually found in pegmatites and cryolite, thomsenolite, Chiolith , elpasolite , Ralstonite , Sellait and fluorite associated .
Only a small number of pachnolite sites are known. The 17 known locations (as of May 2010) include the type locality Ivittuut on Greenland , Cerro Blanco in Argentina , Pedra Lavrada in Brazil , Pleystein and Hagendorf in Bavaria ( Germany ), Gjerdingselva in Norway , the Ilmen Mountains in Russia and Cheyenne Mountain , Tampa Bay , Gillis Range and Winterham in the United States .
See also
literature
- Pachnolite. In: John Williams Anthony et al .: Handbook of Mineralogy. Volume 1. Mineral Data Publishing, Tucson, Ariz. 1990, ISBN 0-9622097-0-8 , p. 101. (pdf; 72 kB)
Web links
Individual evidence
- ↑ a b Pachnolite at mindat.org
- ↑ a b c Pachnolite. In: Anthony et al .: Handbook of Mineralogy. 1990, 1, p. 101.
- ↑ A. Knop: About Pachnolith, a new mineral. In: Liebig's annals of chemistry. 1863, 127, pp. 61-68, doi : 10.1002 / jlac.18631270108 .
- ↑ Systematics of the minerals according to Dana - halides