The Rain occurrence is located 13 kilometres northeast of Aiken Lake in the northeastern part of the Lay Range, between the Mesilinka and Swannell rivers, approximately 98 kilometres northwest of the community of Germansen Landing.

The hostrock is a northwest striking, southwest dipping, thickly bedded, grey limestone overlying quartzose sandstone, grit, and green argillite. The carbonate is overlain by a thin black carbonate unit succeeded by slate and graphitic argillite. The hostrocks are not known with certainty but are thought to be part of the Lower Cambrian Atan Group (Mount Kison Formation limestone).

Tan dolomitic zones are developed in the grey limestone unit and lead-zinc-barite mineralization occurs in a creamy white, coarsely crystalline phase of the dolomite (Assessment Report 4607). Two showings are known. The "A" showing consists of a layer of disseminated galena, honey coloured, fine-grained sphalerite and minor pyrite in a banded massive limestone. In 1973, a grab sample assayed 0.82 per cent lead, 3.68 per cent zinc, 3.4 grams per tonne silver and 14.5 per cent barium (Assessment Report 4607). The "B" showing is located 750 metres east-southeast of the "A" and is exposed over a length of 210 metres in three trenches. Although not continuous, the mineralization is exposed over a width of 9 metres. One hand sample assayed 4.53 per cent lead, 4.20 per cent zinc, 3.12 grams per tonne silver and 31.0 per cent barium (Assessment Report 4607).

In 1972-73, Serem Ltd. conducted a program of geochemical soil sampling (181) and geological mapping.