The Nunn Lake uraninite pegmatite is a large, well zoned sill-like body. Uraninite occurs within the outer three feet of the wall zone, as sheet-like masses within an aplitic phase of the pegmatite, and as late fracture fillings.Deposition of the uraninite took place in two stages. The first stage was crystallization within and contemporaneous with the potassium-rich wall zone. The second stage was the crystallization of the uraninite within aplitic phases of the pegmatite and as late fracture fillings. This second stage of uraninite crystallization is in direct association with a mineral assemblage that is evidence of a late residua of alkali potassium silicate and the acid radicals of the halides.

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