Magnesite forms a bed which is conformably interbedded with quartzites of the Lower Cambrian Cranbrook Formation. It is underlain by a sequence of thinly banded, reddish quartzitic and buff magnesite beds and is overlain by magnesite interstratified with thin, greenish argillite beds and locally thin limestone. It varies from coarse to finely crystalline, weathers rough and commonly has a rusty brown surface. Fresh surfaces are pearly grey, white or cream-coloured and are cut by minor quartz veins or host to knots of quartz. The best bed of magnesite is about 15 metres thick and samples indicate the following chemistry: 4.54 per cent SiO2, 2.4 per cent Fe2O3, 0.4 per cent Al2O3, 0.79 per cent CaO, 43.7 per cent MgO and 48 per cent Loss On Ignition.
Minor production has been reported for the Marysville deposit (Z.D. Hora, personal communication, 1990), but no figures are available.