Eosphorite
| Eosphorite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Mn 2+ Al [(OH) 2 | PO 4 ] • H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DD.20 ( 8th edition : VII / D.14) 07.22.01.02 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Cmca (No. 64) |
| Lattice parameters | a = 6.9263 Å ; b = 10.4356 Å; c = 13.5234 Å |
| Formula units | Z = 8 |
| Twinning | according to {100} and {001} |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 3.06 to 3.08; calculated: 3.04 |
| Cleavage | indistinct after {100} |
| Break ; Tenacity | uneven to slightly scalloped |
| colour | colorless, white, pink, brownish (also greenish) |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, fat gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.628 to 1.644 n β = 1.648 to 1.673 n γ = 1.657 to 1.679 |
| Birefringence | δ = 0.029 to 0.035 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 45 to 50 °; calculated: 54 to 66 ° |
| Pleochroism | visible: x = yellow, y = pink, z = light pink to colorless |
Eosphorite is a rather seldom occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the idealized chemical composition Mn 2+ Al [(OH) 2 | PO 4 ] · H 2 O, so it is a water-containing manganese - aluminum phosphate with additional hydroxide ions .
Eosphorite forms a mixed crystal series with childrenite (Fe 2+ Al [(OH) 2 | PO 4 ] · H 2 O) , so in naturally formed eosphorite a small proportion of the manganese is usually replaced ( substituted ) by iron , which is why the formula is indicated in various sources as (Mn, Fe) Al [(OH) 2 | PO 4 ] · H 2 O.
In its pure form, eosphorite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and take on a pink to brownish color due to foreign admixtures, whereby the transparency decreases accordingly. On the dash panel , however, he always leaves a white line. The mineral develops short to long prismatic crystals that can reach a length of up to 20 centimeters and whose surfaces have a glass-like to fat-like sheen . Usually the crystals are grouped into radial to spherical mineral aggregates , the mineral can also appear in coarse, massive aggregates.
Etymology and history
Eosporite was first discovered in the Branchville quarry in Fairfield County of the US state Connecticut and described in 1878 by George Jarvis Brush and Edward Salisbury Dana , who derived the mineral from the ancient Greek word Ἑωσφόρος [Eosphoros] (“Bringer of the dawn ") Named for the morning star (see also Eos , Greek goddess of the dawn and mother of the morning star)
The type material of the mineral is kept at Yale University New Haven (Connecticut, USA) (Register No. 3.3231, 3.5847).
classification
In the 8th edition of the mineral systematics according to Strunz , which is outdated, but still in some cases in use , the eosphorite belongs to the department of “water-containing phosphates with foreign anions ”, where together with Childrenit and Ernstit the “Childrenit series” with system no. VII / D.14 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 eosphorite to the category of “phosphates etc. with 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 other anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4 = 2: 1 ”can be found, where the“ Childrenit group ”with the system no. 8.DD.20 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the eosphorite to the class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates etc., with hydroxyl or halogen" and here it is also together with Childrenit and Ernstit as well as additionally with Sinkankasit in the " Childrenit group " with the system no. 42.07.01 within the sub-section "Water-containing phosphates etc., with hydroxyl or halogen with (AB) 5 (XO 4 ) 3 Z q × x (H 2 O)".
Modifications and varieties
As Childro-Eosphorit is a mixed crystal of Childrenit and Eosphorit referred to, wherein the mixing ratio of 1: 1. This variety was described from Hagendorf near the market town of Waidhaus in Bavaria.
Education and Locations
Eosphorite is usually secondary to some phosphate- containing granitic pegmatites . At its branchville type locality , the mineral occurred in paragenesis with dickinsonite , lithiophilite , rhodochrosite and triploidite . In various quarries near Newry in Oxford County in the US state of Maine, however, Eosporite was also found associated with albite , apatite , beryllonite , cookite , hydroxyl herderite and tourmaline .
In Germany, Eosporite has so far only been found on the Hennenkobel (also Hühnerkobel ), near Erbendorf -Hopfau and Hagendorf / Waidhaus in Bavaria and on the Greifensteinen near Ehrenfriedersdorf in Saxony.
As a rather rare mineral formation, eosphorite can sometimes be abundant at different sites, but overall it is not very common. Around 120 sites are known to date (as of 2013). The "João Modesto dos Santos" pit in the municipality of Mendes Pimentel in the Brazilian state of Minas Gerais , where well-formed crystals of up to 10 centimeters in length emerged, is known for its extraordinary eosphorite finds.
Other locations include Afghanistan, Argentina, Australia, Brazil, Finland, France, Italy, Japan, Canada, Kazakhstan, Mozambique, Namibia, Pakistan, Portugal, Russia, Rwanda, Sweden, Spain, the Czech Republic, Uganda and other states of the UNITED STATES.
Crystal structure
Eosphorite crystallizes orthorhombically in the space group Cmca (space group no. 64) with the lattice parameters a = 6.9263 Å ; b = 10.4356 Å and c = 13.5234 Å and 8 formula units per unit cell .
use
Eosphorite crystals are rarely of high quality and, with a Mohs hardness of 5, are not hard enough for commercial use as a gemstone . For collectors, however, they are occasionally offered in different shapes .
See also
literature
- George Jarvis Brush , Edward Salisbury Dana : On a new and remarkable mineral locality in Fairfield County, Connecticut; with a description of several new species occurring there. First Paper, In: American Journal of Science and Arts. (1878), Volume 116, pp. 33-46 ( PDF 1.2 MB )
Web links
- Mineral Atlas: Eosphorite (Wiki)
- Database-of-Raman-spectroscopy - Eosphorite
- American-Mineralogist-Crystal-Structure-Database - Eosphorite
Individual evidence
- ↑ Webmineral - Eosphorite
- ↑ a b c d Giacomo Diego Gatta, Gwilherm Nénert, Pietro Vignola: Coexisting hydroxyl groups and H 2 O molecules in minerals: A single-crystal neutron diffraction study of eosphorite, MnAlPO4 (OH) 2 H2O. In: American Mineralogist 2013, Volume 98, pp. 1297–1301 doi : 10.2138 / am.2013.4438
- ↑ a b c d e f Eosphorite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.8 kB )
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 649 (first edition: 1891).
- ↑ a b c d Mindat - Eosphorite
- ^ 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. 504 .
- ↑ 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. 635 .
- ↑ Mindat - Number of localities for eosphorites
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 ( Dörfler Natur ).
- ↑ Find location list for eosphorite in the Mineralienatlas and in Mindat
- ^ Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich et al. 2002, ISBN 3-405-16332-3 , p. 234 .