Fig. 3
From: High-altitude erratics in the Bernese Alps (Switzerland)
a Medium-grade metamorphic quartzite boulder (0.7 m) from the Stockesee sediment. b Thin section of the same boulder: quartz grains appear as black, grey and white patches, the coloured ones are mica lamellae. The recrystallized quartz grains have been partly aggregated by grain-boundary-migration marked additionally by the lobate shape of the grain boundaries. The structure and the average size of the recrystallized grains (ca. 83 μ) resulted from a metamorphic temperature of 500–600 °C, according to the method of Stipp et al. (2002)