gadoliniteY

Gadolinite is a rare-earth silicate mineral belonging to the gadolinite group. It forms part of the complex silicate family and contains rare earth elements (REEs) along with iron and beryllium. The mineral occurs in several varieties, of which gadolinite-(Y) is the yttrium-dominant member. The general chemical concept is often written as RE2FeBe2Si2O9, where RE represents rare earth elements such as yttrium (Y), cerium (Ce), lanthanum (La), and neodymium (Nd). Different endmembers are named gadolinite-(Ce), gadolinite-(La), gadolinite-(Nd), gadolinite-(Y), etc.

Gadolinite-Y specifically indicates that yttrium is the most abundant rare earth element in the mineral’s REE site. The mineral was named after the Finnish chemist Johan Gadolin, who studied yttrium, and its type locality is the Ytterby quarry near Stockholm, Sweden. The naming convention reflects the dominant REE in the crystal.

Occurrence and associations: gadolinite occurs most often in granitic pegmatites and in hydrothermal veins. It is commonly found alongside other rare-earth minerals such as xenotime and monazite, and may be associated with zircon and beryl. Crystals are typically elongated and prismatic, with a black to brownish-black color and a vitreous to resinous luster. It has moderate hardness on the Mohs scale, generally around 6, and is usually opaque in hand specimens.

Economic and research context: gadolinite is not a major ore today, but historically it served as an early source of yttrium and other rare earth elements. It remains of interest to mineralogists studying REE patterns in pegmatites and the mineralogy of rare-earth deposits.