Strontiomelan
| Strontiomelan | |
|---|---|
| General and classification | |
| other names |
IMA 1995-005 |
| chemical formula | Sr (Mn 4+ 6 Mn 3+ 2 ) O 16 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.DK.05a ( 8th edition : IV / D.08) 07.09.01.05 |
| Similar minerals | Crypto melan |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic, 2 / m |
| Space group | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 10.00 Å ; b = 5.758 Å; c = 9.88 Å β = 90.64 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 4-4.5 |
| Density (g / cm 3 ) | calculated: 4.66 |
| Cleavage | imperfect |
| Break ; Tenacity | none |
| colour | black, gray |
| Line color | sepia, brown |
| transparency | opaque |
| shine | metallic matt |
| Crystal optics | |
| Pleochroism | strong gray-white |
Strontiomelan is a very rare mineral from the mineral class of oxides and hydroxides . It crystallizes in the monoclinic crystal system with the chemical composition Sr (Mn 4+ 6 Mn 3+ 2 ) O 16 . It occurs in aggregates 100 to 200 μm thick in connection with various minerals.
Etymology and history
Strontiomelan was discovered in 1999 in Saint-Marcel , Aosta Valley , Italy . It is named after its constituent strontium and its black color, in Greek "Melanos".
classification
In the outdated but still in use 8th edition of the systematics of minerals according to Strunz , strontiomelan is classified in the mineral class of oxides and hydroxides. This is based on the ratio of metal to oxygen, so that the mineral is, according to its formula, in the group "Oxides with a ratio of metal : oxygen = 1: 2 (MO 2 and related compounds)". There is the Strontoimelan in the "cryptomelan group", together with Cesàrolith , Coronadit , Henrymeyerit , Hollandit , Manjiroit , Mannardit , Priderit , Redledgeit and Kryptomelan. The mineral ankangite , which was formerly also part of this , has been a variety of mannardite since it was discredited in 2012 .
In the comprehensively revised 9th edition of the Systematics of Minerals according to Strunz , which is also used by the International Mineralogical Association (IMA), the mineral is also classified in the class of oxides and hydroxides. This is initially also subdivided according to the ratio of metal to oxygen. Cryptomelan is also in the group "Metal: Oxygen = 1: 2 and comparable". However, this is now further subdivided according to the size of the cations involved so that the mineral falls into the subgroup “With large (± medium-sized) cations; Tunnel structures "can be found. There he is also part of the "cryptomelan group", but now Romanèchit , Kryptomelan and Todorokit belong to it.
In the systematics of minerals according to Dana , cryptomelan is classified in the group of "multiple oxides" (No. 07). There it is classified in the subgroup of system number 09 (which is also called "multiple oxides"). Within this, strontiomelan also forms a "cryptomelan group" with hollandite, manjiroite, coronadite, kryptomelan and henrymeyerite. It has the system number 07.09.01.05
Crystal structure
Strontiomelan crystallizes monoclinically in the space group P 2 1 / n (space group no. 14, position 2) with the lattice parameters a = 10.00 Å , b = 5.758 Å and c = 9.88 Å as well as two formula units per unit cell .
Education and Locations
Strontiomelan with Braunit , cryptomelane, hollandite, quartz, arsenic -containing fluorapatite , antimony -containing titanite , Jadeit and Strontiopiemontit ( Piemontit with Sr content) associated .
Only three locations are known of strontiomelan. The type locality in Italy is in the autonomous region of Aosta Valley in Saint-Marcel. In addition, a site in Belgium in the province of Luxembourg and a site in Japan in the Kyushu region near the city of Nagasaki are known.
See also
literature
N. Meissner, EA Perseil, J. Brugger, PJ Chiappero: Strontiomelane, SrMn (super 4+) 6 Mn (super 3+) 2 O 16 , a new mineral species of the cryptomelane group from St. Marcel-Praborna, Aosta Valley , Italy In: Canadian Mineralogist , Vol. 37, Part 3, 1999, pp. 673–678 ( PDF , English)
Web links
Individual evidence
- ↑ a b c d e f g N. Meissner, EA Perseil, J. Brugger, PJ Chiappero: Strontiomelane, SrMn (super 4+) 6 Mn (super 3+) 2 O 16 , a new mineral species of the cryptomelane group from St. Marcel-Praborna, Aosta Valley, Italy In: Canadian Mineralogist , Vol. 37, Part 3, 1999, pp. 673–678 ( PDF , English)
- ↑ a b c d Mindat - Strontiomelane
- ↑ Mineral Atlas: Strontiomelan