Bastnäsite-(Ce)
Current inventory:  0 gems
 

  
Bastnäsite is named after the Bastnäs mine, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden where it was originally discovered.

Discovered in 1841;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ce(CO₃)F

Cerium Carbonate Fluoride

Molecular Weight:

219.12 gm

Composition:

Cerium

63.94 %

Ce

74.90 %

Ce₂O₃

Carbon

5.48 %

C

20.08 %

CO₂

Oxygen

21.90 %

O

Fluorine

8.67 %

F

8.67 %

F

-

- %

F

-3.65 %

-O=F₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Carbonates

Strunz 8th Ed. ID:

5/C.07-30

Nickel-Strunz 10th Ed. ID:

5.BD.20a

5 : CARBONATES (NITRATES)
B : Carbonates with additional anions, without H₂O
D : With rare earth elements (REE)

Related to:

Bastnäsite Group. Cerium analogue of Bastnäsite-(La) and Bastnäsite-(Y). Fluorine analogue of Hydroxylbastnäsite-(Ce). Bastnäsite-(Ce)-Hydroxylbastnäsite-(Ce) Series. 4H, 6R, 3R polytypes.

Members of Group:

Bastnäsite Group: Bastnäsite-(Ce), Bastnäsite-(La), Bastnäsite-(Y)

Varieties:

None

Synonyms:

Bastnaesite, Basic Fluocerine, Basikfluorcerium, Basiskfluor-cerium, Bastnaesite-(Ce), Buszite, Hamartite, Hemartite, Hydrocerite (of Glocker), Hydrofluocerite, Kischtimite, Kischtim-Parisite, Kyshtymoparisite, Sub-fluate of cerium

Crystal Data

Crystallography:

Hexagonal - Ditrigonal Dipyrimidal

Crystal Habit:

Commonly in tabular to equant crystals, may be modified, horizontally striated, may be elongated, commonly in syntaxic intergrowth with röntgenite-(Ce), synchysite-(Ce), parisite-(Ce), or cordylite-(Ce), to 20 cm; granular, massive.

Twinning:

None

Physical Properties

Cleavage:

Imperfect on {1011}, Indistinct on {0001}

Fracture:

Uneven

Tenacity:

Brittle

Moh's Hardness:

4.0 - 4.5

Density:

4.90 - 5.20 (g/cm³)

Luminescence:

Dark red Cathodoluminescence

Radioactivity:

Weak; GRapi = 60,386.61 (Gamma Ray American Petroleum Institute Units)

Other:

Strongly Piezoelectric. Soluble in strong, hot acids. May be found as pseudomorphs after Fluocerite or Tscheffkinite.

Optical Properties

Color:

Wax Yellow, Honey Yellow, Reddish Brown

Transparency:

Transparent to Translucent

Luster:

Vitreous to Greasy, Pearly

Refractive Index:

1.717 - 1.823  Uniaxial ( + )

Birefringence:

0.1010

Dispersion:

0.013

Pleochroism:

Weak; faintly pleochroic when absorption E is greater than O.

Occurances

Geological Setting:

The most abundant REE-bearing mineral, typically hydrothermal, although primary igneous occurrences are known. In granite and alkali syenites and pegmatites; in carbonatites; in contact-metamorphic deposits; rarely as a detrital mineral in placers.

Common Associations:

Allanite-(Ce), Cerianite-(Ce), Cerite-(Ce), Fluocerite-(Ce), Fluorite, Parisite-(Ce), Synchysite-(Ce).

Common Impurities:

None

Type Locality:

Bastnäs mines, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden

Year Discovered:

1841

View mineral photos:

Bastnäsite mineral photos and locations

Unusual Gem Categories

Piezoelectric Gems

More Information

Mindat.org
Webmineral.com

Bastnäsite (also spelled Bastnaesite) is an extremely rare gem and one of the few rare earth element (REE) carbonate minerals. Bastnäsite may be weakly radioactive as defined in 49 CFR 173.403 (greater than 70 Bq/gram) due to the presence of the rare earth element (REE) Cerium (64%). Bastnäsite and Monazite both contain Cerium (Ce) and are the two largest sources of Cerium. Gems are usually small and moderately included.

Bastnäsite is one of the unusual minerals that exhibit the piezoelectric effect. Piezoelectricity is the ability of some mineral crystals to generate a voltage in response to applied mechanical stress such as an external pressure. Piezoelectricity was discovered in 1880 by French physicists, brothers Jacques and Pierre Curie.

Bastnäsite distribution: Shinwaro, Kunar Province, Afghanistan; Mont Saint-Hilaire, Quebec, Canada; Andakatany, Ambatofangehana, Madagascar; Zegi Mountain, Fata, Pakistan; Karonge, Burundi; Wigu Hill, Tanzania; Nkombwa Hill, Zambia; and several locations in the USA including near Stove Mountain, in the St. Peters Dome area, and at Crystal Park, near Pikes Peak, El Paso County, Colorado.
 

  
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