PHOTOMICROGRAPH

Crystalline-Clast Breccia
with Melt Matrix

Sanidine Grain

M-1 Core--331 feet

Dark matrix is melt-rock; mottled grain (right) is shocked, partially melted and recrystallized quartz; sanidine grain recrystallized from melted feldspar in the impact melt; similar grains yielded a 74 Ma age for the Manson impact.

field 3.2 x 2.1 mm
cross-polarized light