Wakefieldite

Wakefieldite ((La,Ce,Nd,Y)VO₄) is an uncommon rare-earth element vanadate mineral. There are four main types described of wakefieldite- wakefieldite-(La), wakefieldite-(Ce), wakefieldite-(Nd), and wakefieldite-(Y), depending upon the dominant rare-earth metal ion present. Wakefieldite has a Mohs hardness ranging from 4 to 5.[2] Wakefieldite forms crystals of tetragonal structure. In terms of crystal structure, it is the vanadate analog of the rare-earth phosphate mineral xenotime. Unlike xenotime, it is more favorable for wakefieldite to contain the lighter rare-earth elements over the heavier ones. Due to the lanthanide contraction, the heavier rare earths have smaller ionic radii than the lighter ones. When the phosphate anion is replaced by the larger vanadate anion, the tetragonal crystal system preferentially accommodates the larger light rare-earth elements.[3]

Wakefieldite
Wakefieldite-(La) on hausmannite
General
Category	Rare-earth mineral
Formula (repeating unit)	((La,Ce,Nd,Y)VO4)
IMA symbol	Wf[1]
Strunz classification	8.AD.35
Crystal system	Tetragonal
Crystal class	Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m)
Space group	I41/amd
Identification
Color	Canary-yellow, pale tan (Wakefieldite-(Y)); Dark red to coal-black, pale yellow to bluish gray (Wakefieldite-(Ce)); Light pink, brown (Wakefieldite-(La)
Crystal habit	Prismatic crystals, pulverulent masses
Cleavage	Good on {100}
Tenacity	Very brittle
Mohs scale hardness	4–5
Diaphaneity	Translucent to opaque
Specific gravity	4.25 (calculated Wakefieldite-(Y)); 4.74 (meas. Wakefieldite-(Ce)
Optical properties	Uniaxial (+)
Refractive index	nω = 2.000, nε = 2.140

Wakefieldite was first described for an occurrence in the Evans Lou mine, St. Pierre de Wakefield, Quebec, Canada[4] and later designated Wakefieldite-(Y).[5]