Editing Xenotime (section)

== Properties ==
Crystallising in the [[tetragonal]] (I4<sub>1</sub>/amd) [[crystal system]], xenotime is typically translucent to opaque (rarely transparent) in shades of brown to brownish yellow (most common) but also reddish to greenish brown and gray. Xenotime has a variable [[crystal habit|habit]]: It may be prismatic (stubby or slender and elongate) with dipyramidal terminations, in radial or granular aggregates, or rosettes. A soft mineral ([[Mohs scale of mineral hardness|Mohs hardness]] 4.5), xenotime is—in comparison to most other translucent minerals—fairly dense, with a [[specific gravity]] between 4.4–5.1. Its [[Lustre (mineralogy)|lustre]], which may be vitreous to resinous, together with its crystal system, may lead to a confusion with [[zircon]] (ZrSiO<sub>4</sub>), the latter having a similar crystal structure and with which xenotime may sometimes occur.

Xenotime has two directions of perfect prismatic [[Cleavage (crystal)|cleavage]] and its [[fracture]] is uneven to irregular (sometimes splintery). It is considered brittle and its [[Streak (mineralogy)|streak]] is white. The [[refractive index]] of xenotime is 1.720–1.815 with a [[birefringence]] of 0.095 (uniaxial positive). Xenotime is [[pleochroism|dichroic]] with pink, yellow or yellowish brown seen in the extraordinary ray and brownish yellow, grayish brown or greenish brown seen in the ordinary ray. There is no reaction under [[ultraviolet]] light. While xenotime may contain significant amounts of thorium or uranium, the mineral does not undergo [[metamictization]] like [[sphene]] or zircon would.