Hibonite

Hibonite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the hexagonal crystal system with the general chemical composition (Ca, Ce) (Al, Ti, Mg) 12O19. The elements in brackets can be represented each other, but are always in the same proportions to the other components of the mineral.

Hibonite usually develops long, prismatic crystals in shades of brown, black and maroon. Its Mohs hardness is 7.5 to 8 and its measured density of 3.84 g / cm ³.

Special Features

As with all Seltenerdmineralien hibonite also contains traces of uranium and thorium. For this reason it is classified as weakly radioactive. He has a specific activity of about 88.2 Bq / g (compared to natural potassium 31.2 Bq / g).

Etymology and history

Was first discovered in 1956 in the hibonite eluvial deposit of Esiva at Maromby, in the district Amboasary region Anosy (Fort Dauphin ) in the province of Toliara in Madagascar and described by Curien, Guillemin and Sternberg Orcel. It was named after its discoverer Paul Hibon.

Classification

In the now outdated nomenclature of minerals according to Strunz ( 8th edition ) of hibonite still belongs to the general ward of the " oxides with molar ratio of metal: oxygen = 2: 3".

The revision of the Strunz'schen Mineral classification in the 9th edition of the class of oxides ( and hydroxides ) was partially divided new and more precise divided by the size of the cations involved in the connection. The mineral is thus correspondingly due to its chemical composition in the department of " oxides with the molar ratio of metal: oxygen = 2: 3, 3: 5 and comparable " and there in the Subsection "With large and medium-sized cations ," where he along with Batiferrit, Barioferrit, Diaoyudaoit, Haggertyit, Hawthorneit, Lindqvistit, magnetoplumbite, Nezilovit, Plumboferrit, Yimengit the unnamed group forms 4.CC.45.

The mostly commonly used in English-speaking classification of minerals according to Dana sorted the hibonite also in the class of oxides, there, however, in the department of " multiple oxides with O19 - groups " where he along with Yimengit and Hawthorneit the hexagonal space group P63 / forms mmc crystallizing group 07:04:01.

Education and Locations

Hibonite formed in metamorphic granulite, gneiss, limestone or pyroxenite. Calcium - and aluminum-rich Hiboniteinschlüsse also come in primitive meteorites as präsolares mineral.

Worldwide could be detected at 23 localities hibonite so far, so any of these Tanezrouft in Algeria; at Charleroi in Belgium; in Xingtai in China; in the Israeli Negev desert; in Efremovka meteorite in Kazakhstan; on Tagish Lake in Canada and Madagascar; in the province of Chihuahua in Mexico; in the " Sove Mine" in the Norwegian county of Telemark, in the Far East and West - Siberian regions of Russia; on Krymka meteorite in Ukraine; Kentucky and Utah in the United States and in South Yemen.

Crystal structure

Hibonite crystallized hexagonal space group P63/mmc with lattice parameters a = 5.613 Å and c = 22.285 Å and two formula units per unit cell.