The volume fraction matrix or cement is sufficiently large in matrix-supported conglomerates or breccias to completely separate clasts. The tiny grains, which fit together like jigsaw puzzle pieces, are 1 gray to white, but overall, chert looks nearly black, with white specks, under crossed polars. There may be a few scattered larger grains of recrystallized quartz and scattered high relief carbonate grains. This is a very porous gravel. This type of cement is an important feature of many bioclastic limestones.
Clasts are undulatory extinguishing quartzite.
Chalcedony is fibrous and forms both columnar aggregates nucleating on clast surfaces and radiating aggregates. It has very low relief, may appear dusty and has 1 interference colors. Some well rounded grains of detrital quartz in matrix. 0.6mm Metaconglomerates are especially informative rocks because the included pebbles provide a more readily interpretable record the sedimentary source rocks than do detrital grains. The detrital quartz grains look glassy in hand specimen.