Brianite

• IMA 1966-030

Brianit is a very rarely occurring mineral from the mineral class of " phosphates, arsenates and vanadates ." It crystallizes in the monoclinic crystal system with the chemical composition Na2CaMg [ PO4 ] 2, and has been able to be lamellar structure of {100} found by negative V-shape or polysynthetic twins crystal only in the form of 0.2 mm diameter crystals.

Etymology and history

Was first found Brianit 1967 in the Dayton meteorite at Dayton (Ohio ) in the U.S. and described by LH Fuchs, E. Olsen and E. P. Henderson, who named the mineral in honor of Dr. Brian Harold Mason, a New Zealand - American geochemists, mineralogists and meteorite scientists, according to this.

Classification

In the old ( 8th edition ) and new classification of minerals according to Strunz ( 9th edition ) of the Brianit belongs to the department of " anhydrous phosphates without foreign anions ." Since the new Strunz'schen Mineral classification, however, this division is precisely divided by the size of the cations. The mineral is now in accordance with the subdivision " of the anhydrous phosphates without foreign anions with medium-sized and large cations " where the unnamed group " 8.AC.30 " he is the only member.

The classification of minerals according to Dana assigns the Brianit also in the class of phosphates, but there in the department of " water clear phosphates, etc., with the general formula A B2 XO4 ", where he was also the only member of the unnamed group 38.01.07 forms.

Education and Locations

Brianit forms as a rare component of phosphate needles in iron meteorites often. In paragenesis with Panethit, for the Dayton meteorite also represents the type locality, but also with albite, enstatite, graphite, kamacite, schreibersite, sphalerite, taenite, troilite, and whitlockite

So far Brianit could be detected only at its type locality, the Dayton meteorite.

Crystal structure

Brianit crystallizes in the monoclinic space group P21 / a with lattice parameters a = 13.36 Å; b = 5.23 Å; c = 9.13 Å and 91.2 ° β =, and four formula units per unit cell.