Xenotime-Y

specimen number:
2133377

location:
Zagi Mt, Khyber Pakhutunkhwa, Pakistan

description:
Very fine example for the species, a loose tetragonal lustrous crystal of xenotime-y. In good condition.

The Zagi Mountain site, located near Hameed Abad in the Peshawar District of the Khyber Pakhtunkhwa province of Pakistan, is a prominent open-cut mining locality known for producing a diverse suite of rare-earth element minerals rather than industrial metals. Geologically, the mountain consists of a highly alkaline granitic gneiss that forms part of the larger Warsak igneous complex, which was emplaced during the late Paleozoic era and later deformed during the Himalayan collision. Tectonic activity generated numerous brittle fractures and miarolitic cavities within the gneiss, allowing low-temperature, fluorine-rich and carbon-rich hydrothermal fluids to crystallize rare accessory minerals. While local tribesmen have engaged in artisanal, small-scale surface pitting and hand-tool extraction across the mountain for decades, targeted specimen mining for rare-earth silicates and oxides accelerated dramatically in the late 1990s, and localized extraction remains continuously active under private, community-based tribal arrangements.

Xenotime-Y is a rare yttrium phosphate mineral that crystallizes in the tetragonal system, typically forming short, prismatic or pyramidal crystals that are yellowish-brown, reddish-brown, or greenish in color. Geologically, it occurs as a primary accessory mineral in granitic pegmatites, alkaline granites, and alpine-type hydrothermal veins, and due to its chemical stability, it frequently concentrates within secondary alluvial placer deposits. The mineral forms a solid-solution series with cheralite and monazite, and it often incorporates significant trace amounts of heavy rare-earth elements such as dysprosium, erbium, and ytterbium, as well as radioactive thorium and uranium. At complex alkaline localities like Zagi Mountain, it occurs within the structural fractures of the host rock, serving as an important diagnostic mineral for geochemists studying the concentration and mobilization of incompatible elements during late-stage hydrothermal events.

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