Pyrite mineral specimens oxidise rapidly when the ferrous disulphide is converted to ferrous and ferric sulphates with consequent increase in volume and thus rupture of the specimen. Altough much information exists in the literature this is largely connected to water-saturated or water-free environments. Work has therefore been undertaken with oxidation rates in more normal situations, which might be a basis for recommended RH conditions for storage. Initial findings suggest that, at below 30% RH, oxidation rates may approach zero with time, but that at above 50% RH this would not happpen until all the pyrites had been consumed. The work will be continued, including studies on samples before and after conservation treatments. B/W photographs.