Euxenite

Euxenite (often euxenite-(Y)) is a complex oxide of yttrium, rare-earth elements, niobium, tantalum, and titanium, with uranium and thorium commonly substituting in. It is typically black to brownish-black with a submetallic to greasy luster and forms prismatic orthorhombic crystals or massive aggregates.

Because it contains uranium and thorium, euxenite is usually radioactive, and the radiation often destroys its crystal structure over time, leaving it metamict (glassy and X-ray amorphous). The name comes from Greek for "hospitable to strangers," referring to the many rare elements it hosts.

It is a significant source of yttrium and other rare-earth and refractory metals, found mainly in granite pegmatites and placers.

Euxenite crystallizes in granite pegmatites, especially rare-element pegmatites enriched in niobium, tantalum, and rare earths, and also accumulates in placer (alluvial) deposits because of its resistance to weathering. It forms during the late, volatile-rich stages of pegmatite crystallization.

It is associated with minerals such as columbite-tantalite, monazite, samarskite, zircon, and feldspars. Important localities include Norway (where it was first described), Madagascar, Brazil, Canada, the United States, and various pegmatite and placer districts in Africa and Asia.

Look for black to brownish-black prismatic crystals or masses with a submetallic to resinous-greasy, sometimes pitchy luster, and a grayish-brown to yellowish streak. Hardness is moderate (Mohs 5.5-6.5).

The most telling property is radioactivity (detectable with a Geiger counter) due to uranium and thorium, often accompanied by a metamict, conchoidally fractured, glassy appearance and sometimes a brownish weathering rind. Look-alikes include samarskite, fergusonite, and columbite; reliable separation usually requires chemical or instrumental analysis. Handle with care and store appropriately because of radioactivity.

Euxenite is an ore of yttrium and other rare-earth elements, as well as niobium, tantalum, and titanium, and it has been mined as a source of these strategically important metals used in electronics, alloys, capacitors, phosphors, and high-tech applications. It can also carry recoverable uranium and thorium.

It is not a gemstone and has no metaphysical tradition. Collectors keep specimens for their rare-element chemistry, but radioactivity means they should be stored safely, in ventilated conditions away from living spaces, and handled with washed hands afterward.