sand - large-grained quartz dune sand from Monastery Beach, Carmel Bay, California in a 250 ml display bottle with ground glass stopper then roughly 160 million years

then roughly 160 million years later weathers to become sand again which locally forms dunes

but it can be subtle

Because kaolinite does not absorb water

These examples were formed during the Pleistocene high-stand of Lake Lahontan

The oldest radiolarian fossils in the cherts lived about 200 million years ago

sand - large-grained quartz dune sand from Monastery Beach, Carmel Bay, California in a 250 ml display bottle with ground glass stopper then roughly 160 million yearsThis sand is interesting because of the large size of its quartz grains for a dune sand. Monastery Beach is fed sand immediately by San Jose Creek and by the Carmel River farther north. The longshore current that moves sand from north to south along Californias coast contributes to this beach, but the size and irregular shapes of these grains tells us that the primary source must be a local and not particularly long drainage, most likely San Jose