Pyrite disease was first noticed at the Redpath Museum in 1951 when the paleontological value of graptolite-bearing shales was completely lost by the decomposition of the iron-bearing sediments to a crumbling white dust. Investigation and treatment of affected mineral and fossil specimens was initiated in 1983. Since then 55 specimens have been treated by neutralization of acidic decomposition products using two specific methods. The preferred treatment involved enclosing the specimen with ammonia vapors (10% ammonium hydroxide in polyethylene glycol 400 to keep the relative humidity low) to neutralize the acidic decomposition products of the pyrite. An alternative method involved immersing the affected specimen in a dilute solution of mono-ethanolamine thioglycollate to neutralize the acid and chelate the iron. In general, the rescue of mineral and fossil specimens suffering from pyrite disease should be approached as an environmental problem. Specimens require storage in areas where 55% relative humidity is not exceeded.