23-Quartzite

Conglomeratic (coarse grained) quartzite, a metamorphic rock consisting mainly of quartz grains of sand size and pebble size. This specimen also contains a few grains of other minerals and rocks. The coarse band of quartz pebbles trending north-south through the boulder indicates that moderately strong currents transported and deposited the original grains. Curved (crescentic) fractures on the south side of the boulder probably are due to impact with other boulders during glacial transport. (Compare with no. 19, no. 21, no. 27, and no. 28.)