Ottensite
| Ottensite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2006-014 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.MA.05 ( 8th edition : II / F.11) 02.13.03.02 |
| Similar minerals | Ottensite |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | hexagonal-pyramidal; 6th |
| Space group | P 6 3 (No. 173) |
| Lattice parameters | a = 14.1758 Å ; c = 5.5712 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3.5 |
| Density (g / cm 3 ) | 4.14 (calculated) |
| Cleavage | no |
| Break ; Tenacity | uneven; brittle |
| colour | red-brown |
| Line color | yellow-brown |
| transparency | opaque, translucent in thin fragments |
| shine | Glass gloss |
| Crystal optics | |
| Refractive index | n >> 1.74 (measured), n = 1.992 (calculated) |
| Optical character | uniaxial positive |
| Pleochroism | faint from orange-red to red |
Ottensite is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the hexagonal crystal system with the idealized composition Na 3 (Sb 2 O 3 ) (SbS 3 ) · 3H 2 O is therefore, chemically speaking, a water-containing sodium - antimony - oxysulphide .
Ottensite is a supergenic product of the weathering of stibnite (antimonite). It forms crust-like aggregates up to 1 mm thick on well-developed, terminated stibnite crystals 5 cm long and 6 mm wide. The ottensite crusts consist of spherical aggregates with a diameter of up to 0.3 mm.
Etymology and history
The mineral ottensite appeared for the first time in 2004, with the entire material very likely coming from a single find with only a few dozen specimens. Originally thought to be cetineite, it turned out after the first analyzes that a new mineral had to be present, which was a synthetic compound known since 1988 with the formula Na 3,6 (Sb 2 O 3 ) 3 (SbS 3 ) (OH) 0, 6 · 2.4H 2 O is similar.
The two Czech mineralogists Jiří Sejkora from the Prague National Museum and Jaroslav Hyršl were able to submit the new mineral to the IMA after intensive and complex analyzes, which recognized it in June 2006 under the number IMA 2006-014. Sejkora and Hyršl named the new mineral as Ottensite after the hobby mineralogist and mineral dealer Berthold Ottens (* 1942), an internationally recognized expert on Chinese minerals and deposits.
Type material (holotype) of the mineral is in the collection of the National Museum in Prague , Czech Republic , under catalog no. PIp 1/2006 kept.
classification
In the now outdated, but still common classification of minerals by Strunz (8th edition) of Ottensit still belonged to the department of "non-metallic sulphides with character" where he along with Cetineit , Kermesit and Sarabauit the unnamed group II / F.11 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 ottensite to the class of "sulfides and sulfosalts (sulfides, selenides, tellurides, arsenides, antimonides, bismuthides, sulfarsenites, sulfantimonites , Sulfbismuthite) ”and there in the section“ Oxysulfosalze ”. Here the mineral is in the subsection “A Oxysulfosalts of alkalis and alkaline earths”, where together with cetineite it forms group 2.MA.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns ottensite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it can also be found together with cetineite in the unnamed group 02.13.03 within the subdivision of " Sulphides - including selenides and tellurides - oxysulphides ".
Chemism
Average values from eight analyzes on ottensite resulted in contents of 7.44% Na 2 O, 0.1% K 2 O, 84.64% Sb 2 O 3 , 7.43% S and 4.60% H 2 O. Normalized to 15 anions per formula unit results in the empirical formula (Na 2.89 K 0.03 ) Σ = 0.92 (Sb 2 O 3 ) 3.03 (Sb 0.93 S 2.79 ) (OH) 0.13 · 3.01H 2 O, which can be idealized to Na 3 (Sb 2 O 3 ) (SbS 3 ) · 3H 2 O.
Ottensite is the sodium-dominant analogue of potassium-dominated cetineite and forms the end member of an at least discontinuous mixed crystal series with cetineite.
Crystal structure
Ottensite crystallizes hexagonally in the space group P 6 3 (space group no. 173) with the lattice parameters a = 14.1758 Å and c = 5.5712 Å as well as two formula units per unit cell .
A single crystal structure analysis has not yet been possible due to the lack of suitable material. In general, the presence of one-dimensional infinite tunnels are parallel to 6 for crystal structures of Cetineit-like component 3 characteristic axis formed by the linkage of SbO 3 - pyramids are formed. In the structure of the cetineite, Na (H 2 O) 6 - octahedron zeolite -like, randomly distributed, sit in this tunnel. The potassium atoms are located inside the tunnel and connect the sulfur atoms of the external SbS 3 pyramids to form a three-dimensional framework. The structure of the synthetic Na analog is identical with the exception of the occupation of the alkali atoms. The splitting of the Sb atoms of the SbS 3 pyramids, connected by a pseudo mirror plane , is also present in both structures. The water molecules are only connected to the atoms of the alkali metals.
properties
morphology
Ottensite from the "Qinglong Mine" forms up to 1 mm thick crusts on up to 5 cm long and 6 mm wide stibnite crystals. The crusts consist of grape-like to spherical aggregates with a diameter of up to 0.3 mm, which are sometimes reminiscent of "red caviar". In most cases the aggregates show a smooth and shiny surface, but in a few cases consist of clear crystals, on which the hexagonal prism {10 1 0} and the base pinacoid {0001} can be recognized. Radial aggregates of well-formed columnar crystals have rarely been observed. Ottensite from the "Miniera di Pereta" forms shiny reddish-brown spheroids with a diameter of up to 0.2 mm, which consist of radially arranged individual crystals. The spheroids are fused together to form grape-kidney or stalactitic aggregates.
physical and chemical properties
The color of the crystals and aggregates of the ottensite is red-brown (in the "Miniera di Pereta" occasionally with a light or dark orange tinge), while their line color is always yellow-brown. The surfaces of the opaque crystals and aggregates, which only show through in splinters, have a glass-like sheen .
No cleavage was found on the crystals of the ottensite . Due to its brittleness, the mineral breaks like amblygonite , with the fracture surfaces being uneven. Ottensite has a Mohs hardness of 3.5 and is therefore one of the medium-hard minerals that are a little easier to scratch with a pocket knife than the reference mineral fluorite . The calculated density for ottensite is 4.14 g / cm³.
Education and Locations
Ottensite is formed in the oxidation zone of antimony-rich ore deposits as a typical supergenic alteration mineral of stibnite. In the "Qinglong Mine", after the stibnite crystals had formed, fluorite crystallized on them. Sometimes the stibnite was partially leached away later, creating cavities between the stibnite and fluorite. The ottensite then crystallized in these cavities, sometimes filling them completely, but often forming spherical aggregates in them. An unidentified amorphous antimony oxide turns the fluorite coatings yellow in some steps. These coatings were sometimes referred to as cervantite, but this has not yet been confirmed analytically. In the “Miniera di Pereta”, ottensite crystallizes directly on stibnite; the mineral assemblage includes Metastibnit , quartz , calcite , Valentinit , Brizziit and Mopungit .
As a very rare mineral formation, Ottensite could only be described from two sites so far (as of 2016). The type locality of the Ottensite is the epithermal antimony gold deposit of the "Qinglong Mine" (Dachang Mine) in the Dachang antimony field, Qinglong County , Qianxinan Autonomous District of Bouyei and Miao , Guizhou Province , China . The second site in the world is the antimony deposit of the "Miniera di Pereta" near Pereta not far from Scansano , Province of Grosseto , Tuscany , Italy .
use
Due to its rarity, ottensite is a sought-after mineral by mineral collectors.
See also
literature
- Marcus J. Origlieri, Thomas A. Laetsch, Robert T. Downs: A note on the paragenesis of ottensite . In: The Mineralogical Record . tape 38 , 2007, p. 83-84 .
- Jiří Sejkora, Jaroslav Hyršl: Ottensite, a new mineral from Qinglong, Guizhou Province, China . In: The Mineralogical Record . tape 38 , 2007, p. 77–81 ( rruff.info [PDF; 2.5 MB ]).
Web links
- Mineral Atlas: Ottensite (Wiki)
- Web mineral - ottensite
- Mindat - Ottensite
- RRUFF Database-of-Raman-spectroscopy - Ottensit
- American-Mineralogist-Crystal-Structure-Database - Ottensit
Individual evidence
- ↑ a b c d e f g h i j k l m n Jiří Sejkora, Jaroslav Hyršl: Ottensite, a new mineral from Qinglong, Guizhou Province, China . In: The Mineralogical Record . tape 38 , 2007, p. 77–81 ( rruff.info [PDF; 2.5 MB ]).
- ↑ a b Mindat - mineral description Schaurteit
- ↑ a b Cesare Sabelli, Izumi Nakai, Shigeo Katsura: Crystal structures of cetineites and its synthetic analogue Na Na 3.6 (Sb 2 O 3 ) 3 (SbS 3 ) (OH) 0.6 * 2.4h 2 O . In: The American Mineralogist . tape 73 , 1988, pp. 398–404 ( rruff.info [PDF; 576 kB ]).
- ↑ a b Marcus J. Origlieri, Thomas A. Laetsch, Robert T. Downs: A note on the paragenesis of ottensite . In: The Mineralogical Record . tape 38 , 2007, p. 83-84 .
- ↑ a b c Erica Bittarello, Fernando Cámara, Marco E. Ciriotti, Alessandra Marengo: Ottensite, brizziite and mopungite from Pereta mine (Tuscany, Italy): new occurrences and crystal structure refinement of mopungite . In: Mineralogy and Petrology . tape 109 , 2015, p. 431-442 , doi : 10.1007 / s00710-015-0375-5 .
- ↑ Mindat - Number of localities for Ottensite
- ↑ a b List of locations for Schaurteit at the Mineralienatlas and at Mindat