Bastnäsite

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Bastnäsite
Category Carbonate mineral
Chemical formula (Ce,La,Y)CO3F
Identification
Color Honey-yellow, reddish brown
Crystal habit Tabular to equant striated crystals, also granular, massive
Crystal system Hexagonal - Ditrigonal Dipyramidal
Twinning Dauphine law, Brazil law and Japan law
Cleavage Imperfect to indistinct
Fracture Uneven
Mohs Scale hardness 4 - 5
Luster Vitreous - greasy
Refractive index nω = 1.717 - 1.722 nε = 1.818 - 1.823
Optical Properties Uniaxial (+)
Birefringence δ = 0.101 max.
Pleochroism Faint
Streak White
Specific gravity 4.95 - 5.0
Diaphaneity Transparent to translucent
Other Characteristics Strongly piezoelectric; dark red cathodoluminescence
References [1][2][3]

The mineral bastnäsite is one of a family of three carbonate-fluoride minerals. There is bastnäsite-(Ce) with a formula of (Ce, La)CO3F. There is bastnäsite-(La) with a formula of (La, Ce)CO3F. There is also bastnäsite-(Y) with a formula of (Y, Ce)CO3F. Most bastnäsite is bastnäsite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnäsite and the phosphate mineral monazite are the two largest sources of cerium and other rare earth elements.

Bastnäsite was first described in 1841 from and named for the Bastnas Mine in the Riddarhyttan district, Vastermanland, Sweden.[2]

Bastnäsite occurs in alkali granite and syenite and in associated pegmatites. It also occurs in carbonatites and in associated fenites and other metasomatites.[1][4]

[edit] References

  1. ^ a b http://rruff.geo.arizona.edu/doclib/hom/bastnasitece.pdf Handbook of mineralogy
  2. ^ a b http://webmineral.com/data/Bastnasite-(Ce).shtml Webmineral
  3. ^ http://www.mindat.org/min-560.html Mindat
  4. ^ http://mineral.galleries.com/minerals/carbonat/bastnasi/bastnasi.htm Mineral Galleries


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