Shape indicates the age of sand grains. Different materials break down at different rates. For example, quartz is very sturdy and takes longer to become sand than the calcium carbonate material of mollusk shells. Younger sand has sharp and angled edges; it needs time and wave action to become rounded. Sand particles that are smooth and well-rounded are evidence that they have been rolled around for awhile.

Wave action is the story told with grain size. The story is simple: small waves move small sand grains around; large waves move large grains. In addition, Aeolian transport, or sand movement driven by winds, shifts the sand around on the beach, shaping and reshaping, covering and uncovering.

Color offers evidence for source materials – sand particles that are clear, tan, gray, or brown might be quartz or feldspar, black or gray particles could be ilmenite (titanium oxide) or magnetite (iron oxide); garnets are red, mica is silvery black or gray, and shells are purple, white, black, or brown.
The chorus from the song “Mountain in my Hand” (on the Only One Ocean CD by the Banana Slug String Band) explains it best:

“I’ve got a mountain in my hand from the rain-washed land; down by the sea now is where I stand, with this mountain in my hand trying to understand; Oh, oh, wonderful sand.”

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Sand: Hold a Mountain in Your Hand