Snow mountainite
| Snow mountainite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1999-027 |
| chemical formula | Bi (Co, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2 |
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.CG.15 ( 8th edition : VII / C.31) 02/40/09/06 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 9.005 Å ; b = 6.211 Å; c = 7.440 Å β = 115.19 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {001}, { 1 11}, { 1 02}, {101} and { 1 01} |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | measured: 5.28 |
| Cleavage | no |
| Break ; Tenacity | shell-like |
| colour | brown to beige or olive brown (depending on the iron content) |
| Line color | pale brown to almost white |
| transparency | transparent |
| shine | Diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 1.930 n β = 1.950 n γ = 1.980 |
| Birefringence | δ = 0.050 |
| Optical character | biaxial positive |
| Axis angle | 2V = calculated: 85 ° |
| Pleochroism | clear to weak: X = brown, Y = Z = pale yellow, depending on the iron content. |
Schneebergite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Bi (Co, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2 and develops only microscopic crystals up to about 0.5 mm in size from tabular to leafy-lamellar habit , which come together to form rosette-shaped aggregates . The color depends on the amount of added iron and varies between yellow-orange and yellowish-brown to olive-brown or beige.
Etymology and history
Schneebergite was first found together with nickel schneebergite in 1999 on the Roten Berg near Schneeberg in Saxony and described by Werner Krause , Heinz-Jürgen Bernhardt , Herta Silvia Effenberger and Thomas Witzke , who named the mineral after its type of locality, Schneeberg. It was recognized as an independent mineral in the same year under the IMA accession number 1999-027 . The test results and the recognized name Schneebergit were published in 2002 in the "European Journal of Mineralogy 14" under the title Schneebergite and nickelschneebergite from Schneeberg, Saxony, Germany: the first Bi-bearing members of the tsumcorite group .
In 1880 the name "Schneebergite" had already been given by Aristides Brezina for a mineral from Schneeberg. More recent studies by Otto Zedlitz and Felix Machatschki in 1932, however, showed that this mineral was identical to the Roméit discovered and described in 1841 except for a slightly increased iron content. This so-called "Schneebergit (after Brezina)" has been considered a variety of Roméit ever since. The rules of the IMA state that a name may be reassigned 50 years after the appropriately named mineral has been discredited. Since 67 years had passed since the discrediting of the Schneebergite (according to Brezina), the new assignment was recognized by the "Commission on New Minerals and Mineral Names", the IMA's examination committee. Type material of this "new" snow mountainite is in the collection of the Museum of Mineralogy and Geology Dresden .
classification
The current classification of the International Mineralogical Association (IMA) counts the Schneebergite to the tsumcorite group with the general formula Me (1) Me (2) 2 (XO 4 ) 2 (OH, H 2 O) 2 , in which Me (1), Me (2) and X different positions in the structure of the minerals of the tsumcorite group with Me (1) = Pb 2+ , Ca 2+ , Na + , K + and Bi 3+ ; Me (2) = Fe 3+ , Mn 3+ , Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ , Mg 2+ and Al 3+ and X = As 5+ , P 5+ , V 5+ and represent S 6+ . To Tsumcoritgruppe include not only Schneebergit still Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite .
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Schneebergit belonged to the mineral class of "phosphates, arsenates and vanadates" and then to the Department of "water containing phosphates without foreign anions " where he along with Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Nickellotharmeyerit , Nickelschneebergit , Phosphogartrellit , Rappoldit , Thometzekit , Tsumcorit , Zinkgartrellit the "Tsumcorit-Gartrellit group" with the system number. VII / C.31 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Schneebergite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral can be classified according to its composition in the subsection “With large and medium-sized cations; RO 4 : H 2 O = 1: 1 "can be found, where together with Cabalzarite, Cobaltlotharmeyerite, Cobalttsumcorite, Ferrilotharmeyerit, Krettnichit, Lotharmeyerit, Manganlotharmeyerit, Mawbyit, Mounanaite, Nickellotharmeyerit, Nickelschneebergit, Thomcorzitgruppe" Tsumcorcite and Tsumcorite System no. 8.CG.15 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Schneebergite to the class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates etc.". Here it is together with cobalt sumcorite, helmutwinklerite, mawbyite, nickel snow mountainite, rappoldite, thometzekite and tsumcorite in the " helmutwinklerite subgroup " with system no. 02/40/09 within the subsection “Phosphates containing water, etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O)”.
Crystal structure
Schneebergite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a = 9.005 Å ; b = 6.211 Å; c = 7.440 Å and β = 115.19 ° and 2 formula units per unit cell .
Education and Locations
Schneebergite forms in the oxidation zone of bismuth deposits . Accompanying minerals include scorodite , barium pharmacosiderite , ferrilotharmeyerite , priceingerite and waylandite .
Apart from the type locality Roter Berg near Schneeberg in Germany, no other location for Schneebergite is known so far (as of 2017). The Schneeberg mountain area in the South Tyrolean Passeier Valley , which is designated as a site of discovery , has since been revised as a false report.
See also
Web links
- Mineral Atlas: Schneebergite (Wiki)
Individual evidence
- ↑ a b c d e Thomas Witzke : The discovery of Schneebergite at www.strahl.org
- ↑ a b c Webmineral - Schneebergite (English)
- ↑ a b c American Mineralogist Crystal Structure Database - Schneebergite (English, 2002)
- ↑ a b c d e f Mindat - Schneebergite (English)
- ↑ GSW GeoScienceWorld - European Journal of Mineralogy; January, February 2002: Schneebergite and nickelschneebergite from Schneeberg, Saxony, Germany
- ↑ Otto Zedlitz: The crystal structures of Romeit and Schneebergite . In: Zeitschrift für Krystallographie . tape 81 , 1932, pp. 253–263 ( rruff.info [PDF; 472 kB ]).
- ^ Felix Machatschki : The Pyrochlore Romeit Group . In: Chemistry of the Earth . tape 7 , 1932, pp. 56-76 .
- ↑ Mindat - Schneebergite (of Brezina)
- ↑ Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , 1998, pp. 179-206 , doi : 10.1127 / ejm / 10/2/0179 .