Oxide mineral
Euxenite Euxenite from
Norway , around 11 cm of size
Category Oxide minerals Formula (repeating unit) (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2 6 IMA symbol Eux[ 1] Strunz classification 4.DG.05 Crystal system Orthorhombic Space group Pcmn (no. 62)Color Black, brownish black, greenish black Crystal habit Massive, anhedral crystals in matrix Twinning Common on [201] Cleavage None Fracture Conchoidal to subconchoidal Mohs scale hardness 5.5 to 6.5 Luster Brilliant submetallic, waxy to resinous on fractures Streak Yellowish, grayish, or reddish brown Diaphaneity Opaque, translucent on thin edges Specific gravity 4.7 to 5 Optical properties Isotropic Refractive index n = 2.06 – 2.24 Other characteristics Metamict – originally crystalline, now amorphous due to radiation damage. Radioactive References [ 2] [ 3] [ 4]
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 (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 (Y,Ca,Ce,U,Th)(Ti,Nb,Ta)2 6 .
Name and discovery
It was first described in 1870 and named for from the Greek (εὔξενος), hospitable or friendly to strangers , in allusion to the many rare elements that it contains.[ 4] [ 3]
Occurrence
It occurs in granite pegmatites and detrital black sands .[ 2]
It is found in many locations worldwide, notably its type locality in Jølster, Sunnfjord, Norway .[ 3] Ural Mountains of Russia ; Sweden ; Minas Gerais , Brazil ; Ampangabe, Madagascar ; Ontario, Canada ; and in Arizona , Wyoming and Colorado in the US.[ 5]
Use
Euxenite is used as an ore of the rare earth elements it contains. Rare large crystals have also been used in jewelry.[ 5]
References
