Euxenite

Euxenite or euxenite-(Y) (a correct mineralogical name) is a brownish black mineral with a metallic luster.

Euxenite
Euxenite from Norway, around 11 cm of size
General
CategoryOxide minerals
Formula
(repeating unit)		(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6
Strunz classification4.DG.05
Crystal systemOrthorhombic
Identification
ColorBlack, brownish black,greenish black
Crystal habitMassive, anhedral crystals in matrix
TwinningCommon on [201]
CleavageNone
FractureConchoidal to subconchoidal
Mohs scale hardness5.5 to 6.5
LusterBrilliant submetallic, waxy to resinous on fractures
StreakYellowish, grayish, or reddish brown
DiaphaneityOpaque, translucent on thin edges
Specific gravity4.7 to 5
Optical propertiesIsotropic
Refractive indexn = 2.06 - 2.24
Other characteristicsMetamict - originally crystalline, now amorphous due to radiation damage. Radioactive
References[1][2][3]

Chemistry

It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6. It is commonly partially amorphous due to radiation damage.

Euxenite forms a continuous series with the titanium rich polycrase-(Y) having the following formula: (Y,Ca,Ce,U,Th)(Ti,Nb,Ta)2O6

Name and discovery

It was first described in 1870 and named for from the Greek (εύξεινος), hospitable or friendly to strangers, in allusion to the many rare elements that it contains.[3][2]

Occurrence

It occurs in granite pegmatites and detrital black sands.[1]

It is found in many locations worldwide, notably its type locality in Jølster, Sunnfjord, Norway.[2] Other locations include the Ural Mountains of Russia; Sweden; Minas Gerais, Brazil; Ampangabe, Madagascar; Ontario, Canada; and in Arizona, Wyoming and Colorado in the US.[4]

Use

Euxenite is used as an ore of the rare earth elements it contains. Rare large crystals have also been used in jewelry.[4]

References
  1. http://rruff.geo.arizona.edu/doclib/hom/euxenitey.pdf Minderal Handbook
  2. http://webmineral.com/data/Euxenite-(Y).shtml Webmineral data
  3. http://www.mindat.org/min-1425.html Mindat
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