Bastnäsite

• Lanthanide Fluorcarbonate

Bastnäsit (English also Bastnaesite ) is the name for a group of minerals from the mineral class of " carbonates and nitrates " (formerly known as carbonates, nitrates and borates ). All Bastnaesite crystallize in the hexagonal crystal system, with the general composition (Ce, La, Nd, Y) [( F, OH ) | CO3 ], that in addition the carbonate complex which, referred to as rare earth metals cerium, lanthanum, neodymium and yttrium from the group of lanthanides as well as additional anions fluoride or hydroxide ions. The Bastnaesite are therefore also called lanthanide Fluorcarbonate.

In nature are found due to the formation of mixed crystals always Bastnaesite with two or more of the rare earth elements in the compound. However, recognized by the International Mineralogical Association (IMA ) at the time, only the end members of the mixing rows with the following idealized composition, which are summarized as Bastnäsitgruppe:

• Bastnäsit - (Ce) - Ce [ F | CO3 ]
• Bastnäsit - (La ) - La [ F | CO3 ]
• Bastnäsit - (Nd) - nd [ F | CO3 ]
• Bastnäsit - (Y) - Y [ F | CO3 ]
• Hydroxylbastnäsit - (Ce) - Ce [( OH) | CO3 ]
• Hydroxylbastnäsit - (La ) - La [ (OH ) | CO3 ]
• Hydroxylbastnäsit - (Nd) - Nd [( OH) | CO3 ]

Is counted also for Bastnäsitgruppe Thorbastnäsit ( THCA [ F | CO3 ] 2.3 H2O).

Bastnaesite are usually found in the form of granular to massive mineral aggregates, but also develop hexagonal crystals with tabular to prismatic habit and crystal - to -fat -like shine. Depending on the composition of the mixed crystals varies the color of the transparent to translucent crystals of wax to honey yellow, brick red to carmine red or reddish brown to dark brown. With a Mohs hardness of 4 to 4.5 Bastnäsit belongs to the medium-hard minerals that are similar to the reference minerals fluorite ( 4) and apatite (5 ) can be scratched with a pocket knife.

Bastnasite, monazite and xenotime part next to the main ores for the recovery of the metals of rare earths.

Etymology and history

Bastnäsit was the first time in an ore mine in Bastnäs near the village of Skinnskatteberg discovered and described in 1841 by the French mineralogist Jean Jacques Nicolas Huot, who named the mineral after its type locality in 1838 in the Swedish province of Västmanland.

Huot already determined during the analysis of the mineral that a large part of the cerium content is replaced with lanthanum ( cerium: lanthanum = 36 %: 24%). In addition, in 1961 discovered EE Vainshtein, LK Pozharitskaya and NV Turanskaya in the rare-earth deposit " Belaya Zima " in the Siberian Sayan another Bastnäsit representative with dominant lanthanum content in the formula, which was accordingly called Bastnäsit - ( La). Due to the already recognized mixed crystal formation, the chemical formula of both minerals in many reference works also with (Ce, La) [ F | CO3 ] | specified or (La, Ce) [ CO3 F].

Hydroxylbastnäsit - (Ce) was first discovered in 1962 in the Vuorijärvi Massif ( Vuoriyarvi ) in the Russo- Finnish region of Karelia and in the so-called " Mochalin Log" at Kyschtym in the Urals and described in 1964 by AS Kirillov.

The discovery and first description of Hydroxylbastnäsit - (La) and Hydroxylbastnäsit - (Nd) followed in 1983 and 1985 by Z. Maksimovic and G. Panto, although the recognition of Hydroxylbastnäsit - ( La) has not yet been confirmed by the IMA / CNMNC, since the publication of the description without examination by the CNMNC was. As a type locality apply here the bauxite deposit " Nissi " in the Greek region of Fthiotida ( Ftiotida ) and Nikšić in Montenegro.

Larger importance was Bastnäsit after a considerable deposit was discovered in an old gold mine at Mountain Pass in California.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Bastnäsit group belonged to the system no. V/C.07 for common mineral class of " carbonates, nitrates and borates " and then to the Department of " water clear carbonates with foreign anions ." In addition to the Bastnäsiten and Hydroxylbastnäsiten however, still include the other members Cebait - (Ce), Cordylit - (Ce), Horváthit - (Y), Huanghoit - (Ce), Kozoit - (La), Kozoit - (Nd), Kukharenkoit ( ce ) Kukharenkoit - (La), Lukechangit ( Ce), Micheelsenit, Mineevit - (Y) Parisit ( Ce), Parisit ( Nd), Qaqarssukit ( Ce), Reederit - (Y) Röntgenit ( ce), Synchisit - (Ce), Synchisit - (Nd), Synchisit - (Y) and Zhonghuacerit - (Ce) to this group.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Bastnäsit group in the newly defined class of " carbonates and nitrates " ( borates now form a separate class ), but there also in the department of " carbonates with additional anions, without H2O" one. However, this is further divided according to the conditions prevailing in the connection, and the bastnasite group metals to the system number. 5.BD.20a is accordingly to be found in the subsection "With rare- earth elements (REE )," and in addition to the Bastnäsiten and Hydroxylbastnäsiten only one Thorbastnäsit to this group.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Bastnäsit group as the outdated Strunz'sche systematics in the common class of " carbonates, nitrates and borates " and there in the department of " Carbonate - hydroxyl or halogen" one. The Bastnaesite ( System-Nr. 16a.01.01 ) and Hydroxylbastnäsite ( System-Nr. 16a.01.02 ) Here each form a separate subgroup within the subdivision " Carbonate - hydroxyl or halogen in the Bastnäsit / Synchisit / Parisitgruppen " to find.

Education and Locations

Bastnäsit is likely to form magmatic carbonatites and pegmatites, but can also be caused by Kontaktmetasomatose. Accompanying minerals occur including various Allanite, Cerite, Fluocerite, Gagarinite, Synchysite and pari site and cerianite - (Ce), fluorite, hematite, quartz and microcline.

So far (as of 2013) are considered to be known around 500 localities for Bastnäsit and 20 Locations for Hydroxylbastnäsit. Main Locations of Bastnäsit are, however, Bayan Obo in China, Mountain Pass in California and Madagascar. The largest known accumulation of rare earth minerals in the world, the Sulphide Queen deposit at Mountain Pass district in California, contains, among other Bastnäsit, which is bound to carbonatite -course and kalireiche intrusions.

Known due to exceptional Bastnäsit discoveries include Andakatany in the region Amoron'i Mania Madagascar and Karonge ( Gakara, Bujumbura ) in Burundi, where up to 20 or 10 centimeters large crystals occurred. Beautifully trained and partially transparent Bastnäsitkristalle could be found especially in the Trimouns talc mine near Luzenac in France and the Zagi Mountain ( Zegi Mountain) in the so-called Federally Administered Tribal Areas (FATA ) in Pakistan.

Bastnäsit is chemically labile weathering, whereby the oxide dissolved and combined with existing phosphates (formation of monazite ).

Hexagonal tafeliger, reddish translucent Bastnäsit - (Ce ) crystal from the same locality ( Size: 1.5 x 1.5 x 0.3 cm)

Brownish Bastnäsit - ( La) - rosettes in a calcite druse from the quarry Jones Mill, Magnet Cove, Hot Spring County, Arkansas, USA ( field of view 3 mm)

Crystal structure

The Bastnaesite crystallize in the hexagonal space group P62c ( Raumgruppen-Nr. 190 ) with the following lattice parameters:

• Bastnäsit - (Ce) - a = 7.12 Å and c = 9.76 Å ° and 6 formula units per unit cell.
• Bastnäsit - ( La) - a = 7.09 Å and c = 9.718 Å ° and 6 formula units per unit cell.
• Bastnäsit - (Y) - a = 6.57 Å and c = 9.48 Å ° and 6 formula units per unit cell.

Although the Hydroxylbastnäsite crystallize also hexagonal, but in the space group P6 ( Raumgruppen-Nr. 174 ) with the following lattice parameters:

• Hydroxylbastnäsit - (Ce) - a = 12.4112 Å and c = 9.8511 Å ° and 6 formula units per unit cell.
• Hydroxylbastnäsit - (Nd) - a = 12.32 Å and c = 9.88 Å ° and 6 formula units per unit cell.

Use and processing

From the Bastnäsiten a large part of the world production is grown in lanthanides since the 1960s. A typical distribution of the rare earth elements on the example of Bastnäsit - (Ce) shows the following table, the exact composition may vary according to the archaeological site.

Bastnäsit is normally digested with acid. The treatment of the unroasted ore with concentrated sulfuric acid liberates hydrogen fluoride and forms insoluble Lanthanoidsulfate, which can then be dissolved and processed in cold water. For the treatment of unroasted ore with dilute sulfuric acid are dissolved lanthanides as sulfates and fluorides bound as a stable cerium IV complex. The production then requires the separation of fluoride by treatment with sodium hydroxide. In the treatment of the ore with hydrochloric acid unroasted at about 100 ° C, the major part of the lanthanides is dissolved as chlorine, but it leaves an insoluble residue lanthanide fluoride. The latter must be converted by treatment with sodium hydroxide in hydroxides, before further processing is possible.

If the Bastnäsiterz is roasted before to remove carbon dioxide and oxidize the available cerium, the main proportion of the lanthanides can likewise be removed by treatment with hydrogen chloride, but the residue still contains significant amounts of insoluble lanthanide and fluorides, and ceric oxide. By treatment of calcined bastnasite with 57 % nitric acid lanthanides are separated off from poorly soluble silica, and barium sulfate. The lanthanides are then recovered from the filtrate by extraction with tri-n- butyl phosphate.