Gypsum outcrops on the southeast flank of Fire Mountain, 1.4 kilometres southwest of the Lillooet River, 14 kilometres northwest of the north end of Harrison Lake.

The showing is hosted in volcaniclastic sandstone and feldspathic greywacke of the third member of the Lower Cretaceous Brokenback Hill Formation, Fire Lake Group.

The gypsum occurs in a 3 to 5 metre thick bed of crumbly, light coloured rock of exhalative origin that has been traced for 100 metres. The bed contains 40 to 60 per cent, fine to medium-grained gypsum, cementing sand. Disseminated pyrite locally comprises up to 15 per cent of the rock. The bed is brecciated in places, where clasts of gypsum are cemented by a second phase of gypsum.