euxenite
{{Short description|Oxide mineral}}
{{Infobox mineral
| name = Euxenite
| category = Oxide minerals
| boxwidth =
| boxbgcolor =
| image = Euxenite - Vegusdal, Norvegia 01.jpg
| imagesize = 260px
| caption = Euxenite from Norway, around 11 cm of size
| formula = {{chem|(Y|,Ca|,Ce|,U|,Th|)|(|Nb|,Ta|,Ti)|2|O|6}}
| strunz = 4.DG.05
| system = Orthorhombic
| symmetry = Pcmn (no. 62)
| color = Black, brownish black, greenish black
| habit = Massive, anhedral crystals in matrix
| twinning = Common on [201]
| cleavage = None
| fracture = Conchoidal to subconchoidal
| mohs = 5.5 to 6.5
| luster = Brilliant submetallic, waxy to resinous on fractures
| refractive = n = 2.06 – 2.24
| opticalprop = Isotropic
| birefringence =
| pleochroism =
| streak = Yellowish, grayish, or reddish brown
| gravity = 4.7 to 5
| diaphaneity = Opaque, translucent on thin edges
| other = Metamict – originally crystalline, now amorphous due to radiation damage. 25px Radioactive
| references = http://rruff.geo.arizona.edu/doclib/hom/euxenitey.pdf Minderal Handbookhttp://webmineral.com/data/Euxenite-(Y).shtml Webmineral datahttp://www.mindat.org/min-1425.html Mindat
}}
Euxenite, or euxenite-(Y) (the official mineralogical name), is a brownish black mineral with a metallic luster.
Chemistry
It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is {{chem|(Y|, Ca|, Ce|, U|, Th|)(Nb|, Ta|, Ti|)|2|O|6}}. It is commonly partially amorphous due to radiation damage.
Euxenite forms a continuous series with the titanium rich polycrase-(Y) having the formula {{chem|(Y|,Ca|,Ce|,U|,Th|)|(|Ti|,Nb|,Ta)|2|O|6}}.
Name and discovery
Occurrence
It occurs in granite pegmatites and detrital black sands.
It is found in many locations worldwide, notably its type locality in Jølster, Sunnfjord, Norway. 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.http://www.galleries.com/minerals/oxides/euxenite/euxenite.htm Mineral Galleries
Use
Euxenite is used as an ore of the rare earth elements it contains. Rare large crystals have also been used in jewelry.