Groutit
| Groutit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | α-MnOOH |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.FD.10 ( 8th edition : IV / F.06) 01/06/01/03 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pbnm (No. 62, position 3) |
| Lattice parameters | a = 4.56 Å ; b = 10.70 Å; c = 2.87 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 3.5 to 4; 5.5 |
| Density (g / cm 3 ) | 4.144 |
| Cleavage | perfect after {010}, good after {100} |
| colour | blue black |
| Line color | dark brown |
| transparency | opaque |
| shine | Diamond luster, faint metallic luster |
Groutite is a seldom occurring mineral from the mineral class of "oxides and hydroxides" with the chemical composition Mn 3+ OOH or α-MnOOH, so it consists in equal parts of manganese in the orthorhombic modification , oxygen and hydroxide ions (OH).
Groutit develops tabular or needle-like, prismatic crystals of a blue-black color. Its streak color is dark brown. The opaque crystals show a diamond-like to slightly metallic sheen on the surfaces . The Mohs hardness is given as 3.5 to 4 or 5.5. Groutit is one of the soft or medium-hard minerals, and it can at least be scratched with a pocket knife.
Etymology and history
Groutit was named in 1945 by its discoverer John W. Gruner after the American petrologist Fitch Grout (1880-1958). The type locality is the open-cast mining pit Mahnomen and Sagamore manganese No. 2 pit in Ironton, Crow Wing County , Minnesota, USA.
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the groutite belonged to the mineral class of "oxides and hydroxides" and there to the department of "hydroxides and oxidic hydrates (water-containing oxides with layer structure)", where it belonged together with Akaganeit , Boehmite , diaspore , feitknechtite , feroxyhyte , goethite , lepidocrocite , manganite , sword mannite and tsumgallite the "Akaganeit group" with the system no. IV / F.06 .
The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and is used by the International Mineralogical Association (IMA), classifies the groutite in the category of "hydroxides (without V or U)". This is further subdivided according to the possible presence of hydroxide ions or water of crystallization and the crystal structure, so that the mineral is classified according to its composition and structure in the sub-section “Hydroxides with OH, without H 2 O; Chains of edge-linked octahedra can be found, where together with Bracewellite , Diaspor, Goethite, Guyanaite , Montroseite and Tsumgallite the “Diaspor group” with the system no. 4.FD.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the groutite to the class of "oxides and hydroxides" and there in the department of "hydroxides and hydroxide-containing oxides". Here he is in the " Diaspor group (Orthorhombic, Pnma or Pnmd) " with the system no. 06.01.01 to be found within the sub-section "Hydroxides and hydroxide-containing oxides with the formula: X 3+ O OH".
Crystal structure
Groutite crystallizes orthorhombically in the space group Pbnm (space group no. 62, position 3) with the lattice parameters a = 4.56 Å ; b = 10.70 Å; c = 2.87 Å and 4 formula units per unit cell .
Modifications and varieties
The compound Mn 3+ OOH is trimorphic and occurs in nature in addition to orthorhombically crystallizing groutite as monoclinically crystallizing manganite (γ-MnOOH) and as trigonal crystallizing feitknechtite (β-MnOOH).
Education and Locations
Groutit comes including in limonite before glands, especially in Germany in the rubble iron ores of the mine Bülten-Adenstedt at Peine in Lower Saxony, where he worked in the Druse with calcite and barite may be associated. In its type locality it occurs as a secondary mineral in limonite glands in the weathering zone of ribbon iron ores . In the Black Water Mine in Apache County and in Holbrooke in Navajo County (both Arizona, USA) it forms long prismatic to stem-like crystals on recrystallized petrified wood ( quartz with abundant hematite deposits).
Other deposits in Germany are in the Rappenloch mine in Eisenbach in Baden-Württemberg, in the limestone quarry of the Hufgard lime works near Hösbach in Bavaria, in the Einheit in Elbingerode , Saxony-Anhalt and near Ilfeld in the southern Harz region of Thuringia.
Web links
- Mineral Atlas: Groutit (Wiki)
- Mindat - Groutite
- Object of the quarter - 05/06: Groutit - rarity from Lower Saxony. In: bgr.bund.de. Retrieved July 14, 2016 .
Individual evidence
- ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 235 .
- ↑ a b c Groutite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 70 kB )
- ↑ a b c Webmineral - Groutite (English)
- ↑ Find location list for groutite at the Mineralienatlas and at Mindat