Fig. 6. Limit curves for conversion of forsterite into olivine. The numbers denote the value of the stoichiometric coefficient x for olivine with composition . The uppermost full line is the stability limit of pure forsterite (). The upper dotted line shows the stability limit of enstatite, the lower one where 90% of the forsterite is converted into enstatite. The dashed line shows the P -T stratification in the central plane of a protoplanetary disk model for comparison.