Orientit
| Orientit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca 8 Mn 3+ 10 [(OH) 10 | (SiO 4 ) 3 | (Si 3 O 10 ) 3 ] • 4H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates - group silicates |
|
System no. to Strunz and to Dana |
9.BJ.05 ( 8th edition : VIII / C.34) 58.03.01.02 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | P 2 mm (No. 25) |
| Lattice parameters | a = 9.04 Å ; b = 6.09 Å; c = 19.03 Å |
| Formula units | Z = 1 |
| Frequent crystal faces | {110}, {001} |
| Physical Properties | |
| Mohs hardness | 4.5 to 5 |
| Density (g / cm 3 ) | measured: 3.05 to 3.33; calculated: 3.48 |
| Cleavage | perfect to imperfect after {001} |
| Break ; Tenacity | brittle |
| colour | reddish brown, chocolate brown, brown-black |
| Line color | brown |
| transparency | transparent to translucent |
| shine | Greasy to weak metallic sheen; matt in inclusions |
| Crystal optics | |
| Refractive indices |
n α = 1.758 n β = 1.776 n γ = 1.795 |
| Birefringence | δ = 0.037 |
| Optical character | biaxial positive |
| Axis angle | 2V = measured: 68 ° to 83 °; calculated: 90 ° |
| Pleochroism | visible: X = red-brown; Y = yellow; Z = brownish yellow |
Orientite is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition Ca 8 Mn 3+ 10 [(OH) 10 | (SiO 4 ) 3 | (Si 3 O 10 ) 3 ] · 4H 2 O, so it is a water-containing calcium - manganese- silicate additional hydroxide ions . Structurally it belongs to the group silicates .
Orientite is transparent to translucent and develops only small, thin-tabular to prismatic or pseudo-hexagonal crystals up to about one millimeter in size, which are usually arranged in radial or rosette-shaped mineral aggregates . Its color varies between reddish brown, chocolate brown and brown-black, and its crystal surfaces have a fat-like sheen to a faint metallic sheen .
Etymology and history
Orientit was first discovered in 1920 at various points in the manganese ore deposits about 10 km south of Bueycito and near Banes in the former Cuban province of Oriente (today a region consisting of five provinces). The mineral was described and published a year later by Donnel Foster Hewett (1881–1971) and Earl V. Shannon, who named it after the area where it was found.
Type material of the mineral is kept in the National Museum of Natural History in Washington, DC (Register No. 93819) and in the Natural History Museum in London (1923,1029).
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the orientite belonged to the mineral class of "silicates and germanates" and there to the department of " group silicates (sorosilicates)", where together with ardennite it formed the "ardennite orientite" Group "with the system no. VIII / C.34 and the other members Ardennit- (V) , Cassagnait , Medait , Saneroit , Scheuchzerit and Tiragalloit .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the Orientit in the category of “group silicates”. However, this is further subdivided according to the structure of the silicate groups and the coordination of the cations involved , so that the mineral can be classified according to its composition in the sub-section “Group silicates with Si 3 O 10 , Si 4 O 11 etc. anions ; Cations in octahedral [6] and / or greater coordination ”can be found, where it is the only member of the unnamed group 9.BJ.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Orientit to the class of "silicates and Germanates", but there in the more finely subdivided division of "group silicates: insular, mixed, individual and larger tetrahedral groups". Here it is together with ardennite (As) and ardennite (V) in the " ardennite group " with the system no. 58.03.01 within the sub-section “Group silicates: insular, mixed, single and larger tetrahedral groups with insular single and triple groups (n = 1.3)”.
Education and Locations
At its type locality in the province of Oriente, the mineral found in manganese-containing ore bodies in Latit - and andesite - tuffs and in volcanic agglomerates and limestone where it in paragenesis with Barite , calcite , manganite , Neotokit , Pyrolusit , quartz and Todorokit occurred.
In the manga mine near Copper Harbor in Keweenaw County in the US state of Michigan also Orientit created by displacement of calcite in Basalt - clefts and - lenses with Braunit and manganite.
In addition, the mineral was previously (as of 2013) only found in the "Lanqiao Mine" near Liancheng in the Chinese province of Fujian, in the "Cerchiara Mine" near Borghetto di Vara in the Italian region of Liguria, in the "Wakasa Mine" in the Okhotsk sub-prefecture on the Japanese island of Hokkaidō, in the cave of giant crystals (cueva de los cristales) in the Naica mine in Mexico, in the "Wessels Mine" near Hotazel in the manganese ore field of the South African Kalahari desert and in quarry 4 of the " Governor Talc Company “ Harrisville in Lewis County of the US state New York.
Crystal structure
Orientite crystallizes isotypically with ardennite in the orthorhombic crystal system in the space group P 2 mm (space group no. 25) with the lattice parameters a = 9.04 Å ; b = 6.09 Å and c = 19.03 Å as well as one formula unit per unit cell .
The crystal structure of Orientit consists in the direction of the c-axis from a regular alternation of two different assemblies. One assembly consists of (SiO 4 ), (Si 3 O 10 ) and (MnO 6 ) groups and the other of (Si 3 O 10 ) and water molecules (H 2 O). The cavities are filled with calcium cations and are in turn connected to seven oxygen atoms.
See also
literature
- DF Hewett, Earl V. Shannon: Orientite, a new hydrous silicate of manganese and calcium from Cuba. In: American Journal of Science. Volume 5, Volume 1, 1921, pp. 491-506. doi: 10.2475 / ajs.s5-1.6.491 ( preview 1st page on ajsonline.org )
- WF Foshag: New minerals. In: American Mineralogist. Volume 6, 1921, p. 132. ( PDF 62.4 kB )
- Charles B. Sclar: Optical crystallography of Orientite from Oriente Provinze, Cuba. In: The American Mineralogist. Volume 46, 1961, pp. 226-232. ( PDF 475.8 kB )
- Orientite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 70.1 kB )
- Marcello Mellini, Stefano Merlino, Marco Pasero: X-ray and HRTEM structure analysis of orientite. In: American Mineralogist. Volume 71, 1986, pp. 176-187. ( PDF 1.3 MB )
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 701 (first edition: 1891).
- Hans Jürgen Rösler : Textbook of Mineralogy . 4th, revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 459, 491 .
Web links
- Mineral Atlas: Orientit (Wiki)
- Database-of-Raman-spectroscopy - Orientite
- American-Mineralogist-Crystal-Structure-Database - Orientite
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 591 .
- ↑ Webmineral -
- ↑ a b c Orientite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 70.1 kB )
- ↑ a b c Mindat - Orientite
- ^ WF Foshag: New minerals. In: American Mineralogist. Volume 6, 1921, pp. 132-132. ( PDF 62.4 kB )
- ↑ James Gilluly (1974): Donnel Foster Hewett 1881-1971. A Biographical Memoir. In: National Academy of Sciences. ( PDF 833.6 kB )
- ↑ Find location list for Orientite at the Mineralienatlas and at Mindat
- ↑ Marcello Mellini, Stefano Merlino, Marco Pasero: X-ray and HRTEM structure analysis of orientite. In: American Mineralogist. Volume 71, 1986, pp. 176–187 ( PDF 1.3 MB )