The Island Moly occurrence is located on a small island on the east side of Atlin Lake, about 15 kilometres north of the community of Atlin.

The only reference to the molybdenite showing is on Map 1082A (Geological Survey of Canada Memoir 307). On this map, the author of the memoir, J.D. Aitken, shows rock cropping out on the island belonging to the Middle Jurassic Fourth of July Creek batholith (Three Sisters Plutonic Suite). In the memoir, it’s mentioned that D.D. Cairnes (1913) originally referred to the rocks as "pink granites" and Aitken (1958) has retained this same terminology. The Fourth of July Creek batholith is a large body covering about 780 square kilometres. It is zoned with three "mappable" phases (Aitken, 1958). These phases, including the pink granite, range from granite to diorite. The pink granite appears to be the youngest phase and crops out primarily along Atlin Lake in the southwest portion of the batholith.

Microcline and orthoclase are both present and the rock can have a porphyritic texture. Thin section shows this rock to commonly have microfractures filled with quartz. This unit can also be very rich in sphene, sometimes easily recognizable in hand specimen.

There is another small molybdenite occurrence on the east shore of Atlin Lake (Norsk, 104N 014), 600 metres directly across from the island.