It might sound obvious, but sand is made from organic materials (like animal skeletons or plant matter) as well as pieces of rock sediment. Over time, water flow breaks these things up... and sand is born! So it’s basically components of what we already consider crystals: lovely minerals of all types (depending on where you live), including tiny crystals and other organic things. Bits of shells, pearls, driftwood, and coral are all contained there.
If you think coral, pearls, and shells all have special properties, sand might be a nice medium to work with. It also contains rocks, minerals... baby crystals. Of course sand has magickal use! Whether wearing a crystal point of pressed sandstone or even just molten glass, you can depend on its good vibes.
After all... sand makes glass and in a lot of cases, the glass we make gets returned to the beach.
In short, sand contains a bit of all elemental forces. It’s merely pieces of our earth tossed and broken by air and water, warmed by a fiery sun and cooled by the light of a million moonlit skies. I don’t know about you, but that sounds like a shitload of magic to me. I use sand bits in some of my crafts for this very reason.