Armalcolite

• Kennedyit

Armalcolit (also Kennedyit ) is a mineral from the mineral class of oxides. It crystallizes in the orthorhombic crystal system with the chemical composition of (Mg, Fe 2 , Al) ( Ti2 , Fe3 ) and developed 2o5 hypidiomorphe only crystallites of about 300 micron size, or granular masses.

Etymology and history

Due to the fact that the mineral was first found in moon rocks, it designated the first to describe 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 according to the initial syllables of names of the three astronauts of the Apollo 11 mission, Armstrong, Aldrin and Collins. The first Fund samples derive from this mission to the moon. The type locality of Armalcolit is according to the Sea of ​​Tranquility. The mineral was later discovered in the world.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Armalcolit belonged to the mineral class of " oxides and hydroxides " and then to the Department of " oxides with the molar ratio of metal: oxygen = 2: 3 ," where he along with pseudobrookite and pseudorutile the " pseudobrookite group " with the system no. IV/C.24 formed.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Armalcolit also in the class of " oxides and hydroxides ," there, however, in the newly defined division of " oxides with the molar ratio of metal: oxygen = 2: 3, 3: 5 and comparable " one. This department is also further divided according to the relative size of the cations involved, so that the mineral is found according to its composition in the subsection "With medium-sized cations " where there along with Mongshanit and pseudobrookite the " pseudobrookite group " with the system No. 4.CB.15 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Armalcolit into the class of " oxides and hydroxides " and there in the department of " multiple oxides ". Here he is with pseudobrookite and a mineral that is only known under the name IMA2000 -016, found in the unnamed group 07:07:01 within the subdivision " multiple oxides with different formulas ."

Education and Locations

Armalcolit formed at low pressures and high temperatures in titanium- rich basalts and MikroBrekzien, rare in granitic pegmatites, ultramafic rocks, Lamproiten or kimberlites. On Earth, the mineral was also found in impact craters or as inclusions in carbonaceous chondrites.

So far Armalcolit was detected beside the Mare Transquillitatis on the moon only at 26 sites on earth: On the sub-Antarctic Kerguelen; the 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 to Sacha and Chatanga; in Brusno / Okres Banská Bystrica in Slovakia; in the Spanish regions Albacete and Murcia; in the South African mines of Jagersfontein and Kimberley; in Liberec / Bohemia in the Czech Republic; and in the counties Garfield ( volcanic rock of the Smoky Butte ), Uvalde, Piute and Sweetwater in the U.S..

Crystal structure

Armalcolit crystallizes in the orthorhombic space group BBMM ( Raumgruppen-Nr. 63) with the lattice parameters a = 9.7762 Å, b = 10.0341 Å and c = 3.7504 Å and four formula units per unit cell.