Sand is basically the tiny particles eroded from the mountains or rock formation closest to the beach you are standing on as well as some other bits and pieces. The three main ingredients common to all the beaches are: quartz, old shell parts, and decayed materials from the sea and land.
I saw the most interesting image of sand gradients going from really dark to really light as one traveled from Maine to Florida. Which makes sense since the chemical make up of those mountain ranges and the biological life in each of those areas is unique.
Someone did ask me if sand was a natural exfoliates our skins – and the answer is basically, yes. There are a lot of natural exfoliates out there and sand is one – in the sense that it helps to remove dead skin cells, like sponges you see for sale. Maybe not the most comfortable – but, certainly one of the most accessible if you get a burn (once mixed with water – it really cools you off, but looks gross).
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Sadly, it is not just sand that’s acting as an exfoliant at the beach. There are also concerns about tiny particles of polyethylene. These little plastic beads are added intentionally as exfoliants to facial washes made by makeup companies. After they get washed down the drain they could end up in watersheds and eventually into the oceans. Once in the ocean, the tiny plastic may be consumed by plankton. These are then eaten by larger animals, and so on, up the foodchain. So remember to be ugly if you want a beautiful planet. Or consider sand as an alternative. (JK, :P)