The J (Lillie M) showing, located immediately to the east of the Fraser River about 20 km south southeast of Williams Lake, occurs within an area underlain mainly by Paleozoic limestone of the Cache Creek Group. The showing comprises pyrolusite in a number of discontinuous chert lenses within grey limestone and are exposed along an east trending zone over a distance of about 150 metres. Pyrolusite has been derived from the weathering of rhodonite of which minor amounts remain within the chert. The chert is thought to be the result of silicification of limestone.

In 1941, a 34-kilogram bulk sample was analysed by the Mines Branch, Ottawa, and found to contain 39.82 per cent manganese dioxide (National Mineral Inventory 092O16 Mn1). Subsequent subsurface exploration failed to define a downward extension of the mineralization.