Mélonjosephit
| Mélonjosephit | |
|---|---|
| General and classification | |
| chemical formula | CaFe 2+ Fe 3+ [OH | (PO 4 ) 2 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BG.10 ( 8th edition : VII / B.23) 10.41.05.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pbam (No. 55) |
| Lattice parameters | a = 9.54 Å ; b = 10.83 Å; c = 6.37 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {001}, {010}, {100} |
| Physical Properties | |
| Mohs hardness | <5 |
| Density (g / cm 3 ) | measured: 3.65 (2); calculated: 3.61 |
| Cleavage | completely after {110}, indistinct after {010} |
| Break ; Tenacity | brittle |
| colour | dark green to almost black |
| Line color | greenish |
| transparency | translucent |
| shine | Glass gloss to resin gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.720 n β = 1.770 n γ = 1.800 |
| Birefringence | δ = 0.080 |
| Optical character | biaxial negative |
| Axis angle | 2V = 80 to 85 ° (measured); 72 ° (calculated) |
Mélonjosephite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition CaFe 2+ Fe 3+ [OH | (PO 4 ) 2 ], so from a chemical point of view it is a calcium - iron- phosphate with hydroxyl groups as additional anions .
Mélonjosephite mostly develops translucent, tabular crystals , but also fibrous aggregates from dark green to almost black in color with greenish streak color . Visible crystal surfaces have a glass-like to resin-like gloss .
Etymology and history
Mélonjosephite was first discovered in the southern Angarf pegmatite near Tazenakht in the Moroccan province of Ouarzazate and described in 1973 by André-Mathieu Fransolet , who named the mineral after Joseph Mélon (1898–1991).
classification
Already in the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Mélonjosephite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates with foreign anions ", where together with Prosperit it was an independent group VII / B.23 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 Mélonjosephite to the class of “phosphates, arsenates and vanadates” and there to the department of “phosphates etc. with additional anions ; without H 2 O “. However, this section is further subdivided according to the size of the cations involved and the molar ratio of the additional anions and the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral is classified in the sub-section “With medium-sized and large cations; (OH, etc.): RO 4 = 0.5: 1 “can be found, where it is the only member of the unnamed group 8.BG.10 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Mélonjosephite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is the only member of the unnamed group 41.10.05 within the sub-section " Anhydrous phosphates etc., with hydroxyl or halogen with (A 2+ B 2+ ) 3 (XO 4 ) 2 Z q ".
Crystal structure
Mélonjosephite crystallizes orthorhombically in the space group Pbam (space group no. 55) with the lattice parameters a = 9.54 Å ; b = 10.83 Å and c = 6.37 Å and 4 formula units per unit cell .
Education and Locations
Mélonjosephite is formed in granitic pegmatites , where it replaces minerals of the alluaudite group and mostly occurs in paragenesis with triphyline .
So far (as of 2011) Mélonjosephite has been found at three other sites in addition to its type locality Tazenakht in Morocco: In the "Siglo Veinte Mine" near Llallagua in Bolivia, near Přibyslavice - Vlkaneč in Okres Kutná Hora in the Czech Republic and pegmatite near Usakos in Sandamab in Namibia.
See also
literature
- Anthony M. Kampf, Paul B. Moore: Melonjosephite, calcium iron hydroxy phosphate: its crystal structure , in: American Mineralogist , Volume 62, pp. 60–66, 1977 ( PDF 715.6 kB )
Web links
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. 454 .
- ↑ a b Webmineral - Mélonjosephite
- ↑ a b c John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Mélonjosephite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.7 kB )
- ↑ a b c d e f Mindat - Mélonjosephite
- ↑ w3sites.net - THE HISTORY OF THE CONGOLESE MINERALOGY