Cerite

• Cerit - (Ce)
• Cerit - ( La)

Cerit - ( La): nw = 1.810 nε = 1.820

Cerit is a collective name for the two rarely occurring cerium-containing minerals Cerit - (Ce) and Cerit - ( La) from the mineral class of " silicates and Germanates ". Both crystallize in the trigonal crystal system, with the chemical composition

• Cerite ( Ce) - (Ce, La, Ca ) 9 ( Fe3 , Mg) [( OH) 3 | SiO3 (OH ) | ( SiO4) 6]
• Cerite ( La) - (La, Ce, Ca ) 9 ( Fe3 , Mg) [( OH) 3 | SiO3 (OH ) | ( SiO4) 6]

And usually develop only small crystals in the millimeter range from reddish brown or pale yellow to pinkish brown in color and gray -white to white stroke color.

There are numerous variants of Cerit in which the element cerium is replaced by lanthanum or yttrium.

Special Features

As with all Seltenerdmineralien includes cerite traces of uranium and thorium. For this reason, the minerals of the Ceritgruppe be classified as weakly radioactive and have a specific activity of about 1403 ( Cerit - (Ce) ) and 1231 Bq / g ( Cerit - ( La) ) on (compared to natural potassium 31.2 Bq / g).

Etymology and history

Both minerals were appointed on the basis of their share of cerium after this.

The later Cerit - (Ce) was first discovered in 1750 at Bastnäs in the Swedish municipality Skinnskatteberg. Axel Frederic CRONSTEDT called the mineral due to its high density " Tung stone ", but Carl Wilhelm Scheele found in the ore from Bastnäs not the other Tung stones occurring, he discovered element tungsten. He described the mineral matter as a " false Tung stone ". William of Hisinger and Jöns Jakob Berzelius examined the wrong Tung stone chemically accurate and finally realized that this must include a previously unknown element, which they named after the dwarf planet Ceres cerium. Accordingly, the mineral was named from them.

Cerit - ( La) could been demonstrated only in 2001 in the " Material'naya studs " in Hackmantal on Yuksporr in Russian Chibinenmassiv. Analyzed and described the mineral by Yakov A. Pakhomovsky, Yury P. Men'shikov, Victor N. Yakovenchuk, Gregory Yu. Ivanyuk, Sergey V. Krivovichev and Peter C. Burns.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz Cerit - (Ce) and Cerit - ( La) belonged to the mineral class of " silicates and Germanates " and then to the Department of " island silicates with tetrahedral foreign anions ( Neso - Subsilikate ) " where they were Törnebohmit - (Ce) and Törnebohmit - (La ) was a separate group together with Kuliokit - (Y).

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns Cerit - (Ce) and Cerit - (La ) is also in the class of " silicates and Germanates " and then in the Department of " island silicates ( nesosilicates ) " a. This division, however, is further subdivided according to present other anions and the coordination of the cations involved, so that the two minerals are found according to their composition in the subdivision of " island silicates with additional anions and cations in most cases and > coordination " where they together with Aluminocerit - (Ce ) are the unnamed group 9.AG.20.

The classification of minerals according to Dana assigns Cerit - (Ce) and Cerit - ( La) in the class of " silicates and Germanates ", There, however, in the already precisely defined division of the " island silicates: SiO4 Groups and O, OH, F and H2O ". Here are the two minerals namesake of the " Ceritgruppe " with the system no. 52.04.06 and the other Member Aluminocerit - (Ce) in the subsection " island silicates: SiO4 Groups and O, OH, F, and H 2 O with cations in and / or > coordination ".

Education and Locations

Cerite form in hydrothermal quartz - barite carbonatite veins with high content of rare-earth metals. Accompanying minerals include aegirine, allanite, anatase, Ankylit - (Ce), Barylith, barite, Bastnäsit, Catapleiit, chabazite - Ca, edingtonite, epidote, fluorite, galena, monazite, quartz, Törnebohmit and uraninite.

Cerit - (Ce) was the world so far (as of 2010) are detected at approximately 40 sites, including, inter alia in South Australia; at Bobritzsch - Hilber village in Germany; Piedmont in Italy; at Bujumbura in Burundi; Ontario and Quebec in Canada; in the Mongolian Altai Mountains; Khomas in Namibia; North Country and Telemark in Norway; Eastern Siberia, the Urals and Kola in Russia; Gauteng in South Africa; in several other regions of Västmanland and Dalarna in Sweden as well as in several regions of California, Colorado, Connecticut and New York in the USA. besides its type locality Bastnäs Mine

Cerit - ( La) has so far been demonstrated only at its type locality Hackmantal in Russia.

Crystal structure

Cerit - (Ce) crystallized trigonal space group R3c ( Raumgruppen-Nr. 161) with the lattice parameters a = 10.78 Å and c = 38.06 Å and 6 formula units per unit cell.

Cerit - ( La) also crystallizes in the space group R3c trigonal, but with the lattice parameters a = 10.75 Å and c = 38.32 Å and 6 formula units per unit cell.