Galaxite

• Manganese spinel

Galaxite (also manganese spinel ) is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the cubic crystal system with the idealized composition Mn2 Al2O4, is so chemically seen a manganese aluminate ( manganese aluminate ). In nature, however galaxite place predominantly with small amounts of divalent iron and magnesium, which the manganese and trivalent iron, which replace the aluminum in the formula in part (substitution). Therefore, the formula is in some sources with ( Mn2 , Fe2 , Mg) (Al, Fe3 ) 2O4 specified.

Galaxite developed only small, usually rounded crystallites ( grains ) up to about half a millimeter in size, rarely octahedral crystals and crystal twins after " Spinellgesetz " ( penetration twins on the octahedral {111 }). In general, the crystals are opaque and black in color with a glass-like sheen on the surfaces. In thin layers and fragments or by transmitted light they can also reddish brown, brownish orange to deep red or golden yellow to be translucent.

Etymology and history

Was first discovered galaxite in Bald Knob deposit at Sparta in Alleghany County in the U.S. state of North Carolina and described in 1932 by Ross and Kerr, who named the mineral after the nearby city of Galax.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the galaxite belonged to the mineral class of " oxides and hydroxides " and then to the Department of " oxides with the molar ratio of metal: oxygen = 3: 4 ," where he, together with hercynite, gahnite and spinel, the independent group IV/B.01 formed.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the galaxite also in the class of " oxides and hydroxides " and there in the department of " oxides with the molar ratio of metal: oxygen = 3: 4 and comparable " one. This division, however, is further divided according to the size of the cations involved, so that the mineral is "With only medium-sized cations " to find according to its composition in the subdivision where it together with Brunogeierit, chromite, Cochromit, Coulsonit, Cuprospinell, Filipstadit, Franklinite, gahnite, hercynite, Jakobsit, Magnesiochromite, Magnesiocoulsonit, Magnesioferrit, magnetite, Manganochromit, Nichromit, Qandilit, spinel, Tegengrenit, Trevorit, Ulvöspinell, Vuorelainenit and Zincochromit the " spinel " with the system no. 4.BB.05 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the galaxite in the class of " oxides and hydroxides ," there but in the department of " multiple oxides " one. Here he is with spinel, hercynite and gahnite in the " aluminum sub- group " with the system no. 07:02:01 within the sub-division of " multiple oxides ( A B2 ) 2X4, spinel group " to find.

Education and Locations

Galaxite forms in carbonate-rich, silica- undersaturated parts converted metamorphic manganese deposits. Accompanying minerals include Alabandin, Alleghanyite, Jacobsite, Katoptrit, Kellyit, Kutnohorit, magnetite, Magnussonit, Manganhumit, Manganosit, Manganostibit, rhodonite, Sonolit, Spessartine and tephroite.

A rare mineral formation galaxite could be proven so far only in a few localities, of which approximately 40 are considered to be known. Apart from its type locality, the mineral occurred in the United States nor in " Corundum Knob " in Clay County (North Carolina ) and in Galax, in the " Hutter Mine" and " Whittles Emery deposit" in Pittsylvania County of Virginia.

In Switzerland, galaxite Among other findings in Furtschellas and Tanatz Alp at Spliigen GR in the canton of Graubünden, and the Pipji glacier near Pipjitälli and Sparrenflue in Täschtal in the canton of Valais.

Other localities lie that in Ghana, Japan (mainly using on Honshu ), Namibia, Romania, Russia, Sweden, Thailand and the United Arab Emirates.

Crystal structure

Galaxite crystallizes in the space group Fd3m ( Raumgruppen-Nr. 227 ) with the lattice parameters a = 8.29 Å, and eight formula units per unit cell.