Phosphosiderite
| Phosphosiderite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | Fe 3+ [PO 4 ] • 2H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8th CD.05 ( 8th edition : VII / C.09) 04/40/03/02 |
| Crystallographic Data | |
| Crystal system | Monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / n (No. 14, position 2) |
| Lattice parameters |
a = 5.329 to 5.330 Å ; b = 9.789 to 5.809 Å; c = 8.710 to 8.714 Å, β = 90.51 ° to 90.60 ° |
| Formula units | Z = 4 |
| Twinning | Penetration twins according to {101} |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | measured: 2.74 to 2.76; calculated: 2.72 to 2.73 |
| Cleavage | clearly on {010}, indistinctly on {001} |
| Break ; Tenacity | Uneven |
| colour | reddish purple, purple, yellow orange, moss green, peach blossom red |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, resin gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.692 n β = 1.725 n γ = 1.738 |
| Birefringence | δ = 0.046 |
| Optical character | biaxial negative |
| Axis angle | 2V = 62 ° |
| Pleochroism | X = light rose red, Y = carmine red, Z = colorless |
| Other properties | |
| Chemical behavior | very soluble in hydrochloric acid , partially soluble in nitric acid |
Phosphosiderite is a rather rare mineral from the mineral class of phosphates , arsenates and vanadates . It crystallizes in the monoclinic crystal system with the chemical composition Fe 3+ [PO 4 ] · 2H 2 O and is therefore a water-containing iron (III) phosphate .
It develops tabular crystals and penetrating twins with a size of up to 2.5 cm, but also occurs in the form of fibrous, radial-radial, grape-like or kidney-shaped mineral aggregates . They are colored in different shades of red and yellow, with pleochroism occurring. The transparent to translucent crystals can be reddish-violet (purple), peach-blossom-red , yellow-orange or moss-green color , depending on the foreign admixture , and have a glass-like to resinous sheen on the surface .
With a Mohs hardness of 3.5 to 4, phosphosiderite is one of the medium-hard minerals and is slightly easier to scratch with a pocket knife than the reference mineral fluorite (Mohs hardness 4).
Etymology and history
The mineral was discovered by Alfred Des Cloizeaux in 1858 . However, he thought it was Hureaulith . The mineral received its name, which is still valid today, phosphosiderite in 1890 from Wilhelm Bruhns and Karl Busz . The name is derived from "Phospho-" for phosphorus and "-sider-" for large Sideros (= iron ).
In 1910, Alfred Lacroix discovered Vilateit , which turned out to be a variety of phosphosiderite. In 1940 Duncan McConnell described clinobarrandite , which was found to be phosphosiderite. The name metastrengite was introduced in 1951 by Clifford Frondel , Harry Berman and Charles Palache in their 7th edition of the Dana System of Mineralogy , as phosphosiderite is an alternative modification to strictite.
Only the name phosphosiderite is recognized by the International Mineralogical Association (IMA).
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the phosphosiderite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions", where together with Kolbeckite , Koninckit , Malhmoodit , Mansfieldit , metavariscite , Paraskorodit , scorodite , strengite , variscite and Yanomamit the Variscit group with the system number VII / C.09 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns phosphosiderite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the size of the cations and the amount of crystal water, so that the mineral is classified according to its composition in the sub-section “With only medium-sized cations; RO 4 : H 2 O = 1: 2 “can be found where it is with Kolbeckite and Metavariscite in the Metavariscite group with the system number 8.CD.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns phosphosiderite to the class of “phosphates, arsenates and vanadates” and there to the section “water-containing phosphates etc.” (No. 40) and there in the sub-group “water-containing phosphates." etc., with A 3+ XO 4 × x (H 2 O) “. Here it can also be found together with Kolbeckite and Metavariscite in the Metavariscite group with the system number 40.04.03 .
Crystal structure
Phosphosiderite crystallizes isotypically to metavariscite monoclinically in the space group P 2 1 / n (space group no. 14, position 2) with the lattice parameters a = 5.329 Å , b = 9.789 Å, c = 8.710 Å and ß = 90.60 ° and four Formula units per unit cell .
The phosphate group ([PO 4 ] 3− ) forms tetrahedral units of four-coordinate phosphorus atoms. The iron atoms are also four-fold coordinated. There are only bonds between iron and oxygen and between phosphorus and oxygen. In theory, both the iron atoms and the phosphorus atoms should now be in the +4 oxidation state, but the real electron distribution is such that phosphorus is five times positive and iron is only three times positive. The water of crystallization molecules are located in a larger cavity, which occurs once per unit cell and is surrounded by iron, phosphorus and oxygen.
Modifications and varieties
The compound Fe 3+ [PO 4 ] · 2H 2 O is dimorphic and occurs naturally as orthorhombic crystallizing strictite in addition to the monoclinically crystallizing phosphosiderite .
A variety of phosphosiderite rich in manganese is called Vilateite .
Education and Locations
Phosphosiderite forms as a secondary mineral to triphyline in pegmatite rocks . It is associated with triphyline, barbosalite , leukophosphite , laueit , hureaulite, strictite and turquoise .
As a rather seldom occurring mineral formation, phosphosiderite can sometimes be abundant at various sites, but overall it is not very common. Around 200 sites are known to date (as of 2015).
The type locality (location of the first description) of phosphosiderite is in Germany in the Kalterborn Mine , Eiserfeld , Siegerland , North Rhine-Westphalia . There are other sites in Germany in Oberwolfach in the Black Forest ( Baden-Württemberg ). There are a few other sites in Bavaria . In Lower Bavaria there is a site in Rabenstein (community Zwiesel ), in the Upper Palatinate there is one in Auerbach , Pleystein , Plößberg , Waidhaus and Waldmünchen . In Hesse there is only one place of discovery, this is in Essershausen , market place Weilmünster , district of Limburg-Weilburg . In North Rhine-Westphalia there are two sites in the Sauerland (in Arnsberg and Meschede ) in addition to the type locality, and there is another site near the type locality in Eiserfeld ( Eisenzecher Zug Mine ). Another German site is located in Schleswig-Holstein in Joldelund , North Friesland district .
There is a well-known site in Austria . This is located in Styria in Herzogberg ( Kindberg municipality ) in the Koralpe mountain range .
In Switzerland there is a place of discovery in the canton of Ticino in Brissago .
There are other locations in Argentina , Australia , Belgium , Brazil , China , Finland , France , Ireland , Italy , Japan , Cameroon , Canada , Colombia , Libya , Madagascar , Morocco , Portugal , Russia , Rwanda , Spain , Sweden , South Africa , the Czech Republic , Hungary , the United Kingdom and the US states of Alabama , Arizona , Arkansas , California , Colorado , Florida , Georgia , Indiana , Maine , Maryland , Nevada , New Hampshire , New Jersey , North Carolina , South Dakota , Utah , Virginia and Wisconsin .
Use as a gem stone
Phosphosiderite is of little importance as a gemstone for commercial use, because with its low Mohs hardness of 3.5 to 4 it is actually too soft and would scratch quickly. In the form of drum stones , cabochons or spherical beads but will be processed occasionally on various pieces of jewelery.
See also
literature
- Willy Bruhns, Karl Busz: Phosphosiderite, a new mineral from the Kalterborn mine near Eiserfeld in Siegenschen . In: Journal for Crystallography and Mineralogy . tape 17 , 1890, p. 555-560 .
- Phosphosiderites . In: Clifford Frondel, Harry Berman, Charles Palache (Eds.): Dana's System of Mineralogy . 7th edition. 1951, p. 796-771 ( rruff.info [PDF]).
- Duncan McConnell: Clinenobarrandite and the isodimorphous series, variscite-metavariscite . In: American Mineralogist . tape 25 , 1940, p. 719-725 ( minsocam.org [PDF]).
Web links
- Web mineral - phosphosiderite
- Database-of-Raman-spectroscopy - Phosphosiderite
- American-Mineralogist-Crystal-Structure-Database - Phosphosiderite
Individual evidence
- ↑ a b c d e Mineralienatlas: Phosphosiderite
- ^ Mindat - Clinobarrandite
- ↑ a b c d e f g Phosphosiderite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy . Mineralogical Society of America, 2001 ( handbookofmineralogy.org [PDF]).
- ↑ a b c d e Mindat - Phosphosiderite
- ^ Commission on new minerals and mineral names . In: Mineralogical Magazine . tape 36 . International Mineralogical Association, 1967, p. 135 ( rruff.info [PDF]).
- ^ A b Paul B. Moore: The crystal structure of metastrengite and it's relationship to strengit and phosphophyllite . In: American Mineralogist . tape 51 . Mineralogical Society of America, 1966 ( minsocam.org [PDF]).
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 640 (first edition: 1891).
- ^ Mindat - Vilateite
- ↑ Mindat - Number of sites for phosphosiderite
- ↑ a b c d List of locations for phosphosiderite in the Mineralienatlas and Mindat
- ↑ realgems.org - Phosphosiderite with examples of cut stones