Santabarbarait
| Santabarbarait | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2000-052 |
| chemical formula | Fe 3+ 3 [(OH) 3 | (PO 4 ) 2 ] • 5H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.CE.80 ( 8th edition : VII / D.48) 42.10.01.02 |
| Crystallographic Data | |
| Crystal system | none, as amorphous |
| Physical Properties | |
| Mohs hardness | not defined |
| Density (g / cm 3 ) | measured: 2.42 |
| Cleavage | no |
| Break ; Tenacity | clamshell; brittle |
| colour | orange brown to light brown; Amber under the microscope |
| Line color | brownish yellow |
| transparency | translucent |
| shine | Glass gloss to fat gloss |
| Crystal optics | |
| Refractive index | n = 1.695 |
| Birefringence | none, as it is optically isotropic |
Santabarbaraite is a very rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition Fe 3+ 3 [(OH) 3 | (PO 4 ) 2 ] · 5H 2 O and is therefore chemically an iron - Phosphate with additional hydroxide ions .
Santabarbaraite is one of the few minerals that, like glass, is one of the amorphous solids , i.e. the atoms in the compound do not form any ordered structures. Accordingly, it is mainly found in the form of irregular, coarse mineral aggregates and grape-shaped crusts, but also forms pseudomorphoses according to Vivianite .
The mineral is translucent and has an orange-brown to light brown color with a yellowish-brown streak color . The mineral surfaces have a glass to grease-like gloss .
Etymology and history
Santabarbarait was first discovered in the Mina Santa Barbara near the municipality of Cavriglia in the Italian province of Arezzo (Tuscany) and on the Wannon River near the Wannon Falls and the city of Hamilton in the Australian state of Victoria . Both sites are therefore considered to be type localities , with the first being the namesake of the mineral.
Santabarbarait was analyzed and scientifically described by Giovanni Pratesi, Curzio Cipriani, Gabriele Giuli and William D. Birch, who submitted their test results and the chosen name for examination at the International Mineralogical Association (IMA) (accession no. 2000-052). The research results and the recognized name were published in 2003 in the “European Journal of Mineralogy” No. 15 under the title Santabarbaraite: a new amorphous phosphate mineral .
The type material of the mineral is kept in the Museo di Storia Naturale (Natural History Museum) in Florence (catalog no. 2862 / RI).
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the santabarbaraite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where together with ferrisymplesite , gutsevichite and Yukonit the unnamed group VII / D.48 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 the Santabarbaraite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral can be classified according to its composition in the subsection “With only medium-sized cations, RO 4 : H 2 O ≤ 1: 2.5 “can be found where it is the only member of the unnamed group 8.CE.80 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the santabarbaraite to the class of "phosphates, arsenates and vanadates" and there in the category of "water-containing phosphates etc., with hydroxyl or halogen". Here it is together with ferrisymplesite in the " ferrisymplesite group " with system no. 42.10.01 within the sub-section "Water-containing phosphates etc., with hydroxyl or halogen with (AB) 3 (XO 4 ) 2 Z q × x (H 2 O)".
Education and Locations
Santabarbaraite forms in clay soils , usually associated with vivianite or metavivianite .
As a rare mineral formation, Santabarbaraite could only be detected at a few sites, whereby so far (as of 2015) a little more than 10 sites are known. Its type locality, the Mina Santa Barbara, is the only known site in Italy to date .
In Germany, the mineral is only known from the Mark mine near Essershausen in the Hessian district of Limburg-Weilburg and from Hagendorf in the Upper Palatinate municipality of Waidhaus .
Other previously known sites include the Wannon River in the Australian state of Victoria , Anloua in the Adamaua highlands in Cameroon and several places on the Kerch peninsula , which forms the easternmost part of the Crimean peninsula in Ukraine.
See also
literature
- Giovanni Pratesi, Curzio Cipriani, Gabriele Giuli, William D. Birch: Santabarbaraite: a new amorphous phosphate mineral. In: European Journal of Mineralogy. Volume 15, No. 1 (2003), pp. 185-192 doi : 10.1127 / 0935-1221 / 2003 / 0015-0185
Web links
Individual evidence
- ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ Data sheet on Santabarbaraite from the Mineralogical Association (PDF 16.8 kB)
- ↑ a b Mindat - Santabarbaraite
- ↑ Mindat - Number of localities for Santabarbarait
- ↑ List of localities for Santabarbarait in the Mineralienatlas and Mindat