Xenotime: The mineral xenotime information and pictures

About

Xenotime describes a group of several closely related phosphates, arsenates, and vanadates composed of rare earth elements. The term is generally used to describe the most common member of the group, Xenotime-(Y), which is the yttrium phosphate end member of this series. Other, rarer members of the Xenotime series include Xenotime-(Yb), Cherovite, and Wakefieldite.
Xenotime may contain radioactive elements in its structure, and therefore may have some level of mild radioactivity. It frequently forms together with Zircon, and may even grow together in the same crystals as epitaxial overgrowths.
The name Xenotime is derived from an odd source. Its name was given by French mineralogist François Sulpice Beudant after the Greek words "Xenos" meaning stranger, and "Time" meaning honor, to debunk the theory proposed by chemist Jacob Berzelius that the yttrium in this mineral is in fact a new, undocumented element.

Identification

Chemical Formula: General Group Formula: (Y,Yb,Ce,La,Nd,Sc)(PO,VO,SO)₄Xenotime-(Y) Formula: YPO₄
Composition: Xenotime Group: Phosphate, vanadate, or arsenate of yttrium, ytterbium, cerium, lanthanum, neodymium, or scandiumXenotime-(Y): Yttrium phosphate, sometimes with thorium and uranium, as well as the lanthanide metals (dysprosium, ytterbium, erbium and gadolinium)
Color: Light to dark brown, yellowish-brown, and orange. Also yellow, reddish-brown, and greenish brown.
Streak: White, light yellow, light brown
Hardness: 4–5
Crystal System: Tetragonal
Luster: Vitreous, resinous
Cleavage: 1,1
Fracture: Splintery
Tenacity: Brittle
Transparency: Translucent to opaque. Transparent in microcrystals.
Specific Gravity: 4.4–5.1
Group: Phosphates; True Phosphates
Rock Type: Igneous, Metamorphic

Rankings

Popularity (1–4): 3
Prevalence (1–3): 3
Demand (1–3): 1

Crystal Forms & Aggregates

In prismatic crystals, usually with pyramidal terminations, sometimes in stepped pyramids. Often bipyramidal, and occasionally twinned. Also radial, dipyarmidal (resembling elongated octahedrons), massive, and grainy.

Other ID Marks

Radioactive when containing uranium or thorium

Striking Features

Crystal habits, heavy weight, and mode of occurrence.

Environment

Granite pegmatites, and metamorphosed gneiss and schists.

Uses

As an ore of yttrium.

Noteworthy Localities

Outstanding crystals of Xenotime, in in large, chocolate-brown crystals (which can resemble rockets) and have Rutile inclusions come from Ibitiara (Novo Horizonte), Bahia, Brazil. Another exceptional locality, that has produced some of the largest crystals of this mineral in prismatic orange crystals, is Zagi Mountain, Peshawar, Pakistan.
Dipyramidal Xenotime crystals have come from the granite pegmatites of Aust-Agder and Vest-Agder, Norway, especially at the Evje-Iveland pegmatite field. Small prismatic crystals with pyramidal terminations were found in a Graphite mine in Amstall, near Mühldorf, Carinthia, Austria.
In the U.S., small, dark brown Xenotime crystals in matrix come from the Big Bertha Mine, Jefferson Co., Colorado; and large crude crystals were found in Clora May Mine, near Buena Vista, Chaffee Co., Colorado. Historical crystals from late 1800's were found in pegmatites on Manhattan Island, New York Co., New York.

Common Mineral Associations

Quartz, Microcline, Albite, Rutile, Muscovite, Biotite, Zircon, Anatase, Monazite

Distinguishing Similar Minerals

Zircon - Higher specific gravity and hardness, poorer cleavage.Monazite - Different crystal habits.Anatase - May be very difficult to distinguish, though usually more blue in color and crystals striated.