Xenotime-(Y)
| Xenotime | |
|---|---|
Xenotime with Rutile
|
|
| General | |
| Category | Phosphate minerals |
|
Formula (repeating unit) |
YPO4 |
| Strunz classification | 8.AD.35 |
| Crystal system | Tetragonal |
| Crystal class | Dipyramidal (4/mmm) H-M symbol: (4/m) |
| Space group | I41/a |
| Identification | |
| Color | Brown, brownish yellow, gray |
| Crystal habit | Prismatic, radial aggregates, granular |
| Cleavage | Perfect [100] |
| Fracture | Uneven to splintery |
| Mohs scale hardness | 4.5 |
| Luster | Vitreous to resinous |
| Streak | Pale brown, yellowish or reddish, to white |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 4.4–5.1 |
| Refractive index | 1.720-1.815 |
| Birefringence | δ = 0.096 |
| Pleochroism | Dichroic |
| Other characteristics | Not Radioactive or luminescent |
| References | |
Xenotime is a rare earth phosphate mineral, the major component of which is yttrium orthophosphate (YPO4). It forms a solid solution series with chernovite-(Y) (YAsO4) and therefore may contain trace impurities of arsenic as well as silicon dioxide and calcium. The rare earth elements dysprosium, erbium, terbium and ytterbium as well as metal elements such as thorium and uranium (all replacing yttrium) are the expressive secondary components of xenotime. Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly radioactive. Lithiophyllite, monazite and purpurite are sometimes grouped with xenotime in the informal "anhydrous phosphates" group. Xenotime is used chiefly as a source of yttrium and heavy lanthanide metals (dysprosium, ytterbium, erbium and gadolinium). Occasionally, gemstones are also cut from the finer xenotime crystals.
The name xenotime is from the Greek words κενός vain and τιμή honor, akin to "vainglory". It was coined by French mineralogist François Sulpice Beudant as a rebuke of another scientist, Swedish chemist Jöns Jacob Berzelius, for the latter's premature claim to have found in the mineral a new chemical element (later understood to be previously discovered yttrium). The criticism was blunted, as over time "kenotime" was misread and misprinted "xenotime". Xenotime was first described for an occurrence in Vest-Agder, Norway in 1824.
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