The Dunbar Creek showings are all alteration (ie. replacement) deposits hosted by the basal member of the Upper Proterozoic Mount Nelson Formation dolomites. Magnesite occurs at six locations, all on or close to known faults. A grab sample (M7) collected close to Dunbar Creek, near a vertical northwest striking fault, contains 41.41 per cent MgO, 2.84 per cent CaO, 47.48 per cent CO2, 3.97 per cent SiO2 and 2.07 per cent Fe (total). The dolomite here is altered to a coarse-grained, highly irregular magnesite zone about 30 metres northeast of the fault.

North of the first site and across Dunbar Creek a low hill of dolomite is partly altered throughout and contains several, irregular patches composed completely of magnesite. A sample (M8) of this material contains 42.28 per cent MgO, 2.67 per cent CaO, 48.28 per cent CO2, 3.22 per cent SiO2 and 1.03 per cent Fe (total).

Several smaller magnesite bodies occur in the immediate area to the main showings.