The former Heydon Bay Gold Mine is located on the northern shore of Heydon Bay on Loughborough Inlet. The workings extend from the beach northward to an elevation of 381 metres.

The most abundant rock type in the area of Heydon Bay is a dark diorite of the Jurassic to Cretaceous Coast Plutonic Complex which is traversed by tongues of granodiorite which extend from the main mass to the west. A quartz vein 0.6 to 1.5 metres wide is found as an off- shoot from a pegmatite dyke. The vein is mineralized with pyrite and small amounts of chalcopyrite. From the beach the quartz vein is traceable for 7 to 9 metres on the surface until it is offset by a later dyke. The possible continuation of the vein along strike is noted in workings at 76, 99 and 381 metres elevation.

The sulphides in the quartz vein near the beach assayed 51.42 grams per tonne gold from sorted ore (Minister of Mines Annual Report 1933, page A256).