Armalcolite
| Armalcolite | |
|---|---|
 |
|
| General and classification | |
| other names |
Kennedyite |
| chemical formula | (Mg, Fe 2+ , Al) (Ti 2+ , Fe 3+ ) 2 O 5 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.CB.15 ( 8th edition : IV / C.24) 07.07.01.02 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | rhombic-dipyramidal 2 / m 2 / m 2 / m |
| Room group (no.) | Bbmm (No. 63) |
| Lattice parameters | a = 9.7762 Å ; b = 10.0341 Å; c = 3.7504 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | <5 |
| Density (g / cm 3 ) | 4.94 |
| Cleavage | Please complete |
| colour | gray, brownish |
| Line color | Please complete |
| transparency | opaque |
| shine | Metallic luster |
Armalcolite (also Kennedyite ) is a mineral from the mineral class of oxides . It crystallizes in the orthorhombic crystal system with the chemical composition (Mg, Fe 2+ , Al) (Ti 2+ , Fe 3+ ) 2 O 5 and only develops hypidiomorphic crystallites of about 300 μm in size or granular masses.
Etymology and history
Due to the fact that the mineral was first found in lunar rocks , the first descriptors named it AT Anderson, TE Bunch, EN Cameron, SE Haggerty, FR Boyd, LW Finger, OB James, K. Keil, M. Prinz, Paul Ramdohr and A. El Goresy 1970 after the initial syllables of the surnames of the three astronauts on the Apollo 11 mission Armstrong, Aldrin and Collins. The first samples come from this moon mission. The type locality of armalcolite is accordingly the Mare Tranquillitatis . The mineral was later discovered on Earth as well.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the armalcolite belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with the molar ratio of metal: oxygen = 2: 3", where it was used together with pseudobrookit and pseudorutil the "pseudobrookit group" with the system no. IV / C.24 .
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 armalcolite to the class of "oxides and hydroxides", but in the newly defined section of "oxides with the proportion of metal : Oxygen = 2: 3, 3: 5 and comparable “a. This section is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With medium-sized cations”, where, together with Mongshanite and Pseudobrookit, the “Pseudobrookit Group” with the system No. 4.CB.15 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns armalcolite to the class of "oxides and hydroxides" and there in the category of "multiple oxides". Here it can be found together with pseudobrookite and a mineral, which is previously only known under the name IMA2000-016 , in the unnamed group 07.07.01 within the subsection “ Multiple oxides with different formulas ”.
Crystal structure
Armalcolite crystallizes orthorhombically in the space group Bbmm (space group no. 63) with the lattice parameters a = 9.7762 Å , b = 10.0341 Å and c = 3.7504 Å as well as four formula units per unit cell .
Education and Locations
Armalcolite forms at low pressures and high temperatures in titanium-rich basalts and micro breccias , less often in granitic pegmatites , ultramafic rocks, lamproites or kimberlites . On Earth, the mineral was also found in impact craters or as inclusions in carbonaceous chondrites .
So far, in addition to the Mare Tranquillitatis on the moon, armalcolite has only been found at 26 sites on earth: On the sub-Antarctic Kerguelen ; at Nördlinger Ries / Bavaria in Germany; at Qeqertarsuaq in Greenland; at El Toro in the state of San Luis Potosí in Mexico; in the Altai Mountains of Mongolia; at Gătaia in Romania; in the Russian regions around Sacha and Chatanga ; in Brusno / Okres Banská Bystrica in Slovakia; in the Spanish regions of Albacete and Murcia ; in the South African mines of Jagersfontein and Kimberley ; near Liberec / Bohemia in the Czech Republic; as well as in the counties Garfield (volcanic rock of the Smoky Butte), Uvalde , Piute and Sweetwater in the USA .
See also
Individual evidence
- ↑ a b c Webmineral - Armalcolite (English)
- ↑ a b American Mineralogist Crystal Structure Database - Armalcolite (Engl., 1977)
- ↑ IMA / CNMNC List of Mineral Names - Armalcolite (English, PDF 1.8 MB, p. 17)
- ↑ American Mineralogist Crystal Structure Database - Armalcolite (Engl., 1977)
- ↑ Mindat - Localities for armalcolite
literature
- Armalcolite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 68.6 kB )
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 521 .
