The concentrations of minerals were studied in decayed, discoloured and clear wood of Aspen using both light and electron microscopes. Kevex X-ray energy spectrometer system and atomic absorption spectrophotometer analyses revealed that the concentration of K, Na, Ca, Mn, Mg were highest in the decayed wood and lowest in clear wood. Discoloured wood showed an intermediate concentration. Only crystalline calcium was present in the decayed wood and phloem. Association of wood rotting fungi seems to be closely related to the accumulation of calcium crystals.