Sand is everywhere....
Sand is a fascinating medium which in our daily use is much wider spread than most of us are aware of. In its natural form sand is a part of many geologic formations: mountains, rivers, lakes, oceans or dunes. Our daily live would look completely different without sand, because we use if for streets, concrete, glass, computers, porcelain, etc.
In geologic cycles mountain ranges are emerging and depending on durability of the minerals they will be crushed down to the size of sand grains by weather influences.
Water transports sand from mountains down to the ocean. Because water acts like a buffer, rivers do rather transport and assort sands than crushing them down..
Ocean beaches consist a mixture of sands brought down by rivers and parts of crushed corals and shells but also forams, sand grains produced by micro organisms.
Wind - the second transport device for sand carries millions of tons of sand over the face of earth and accumulates them to dunes and sand deserts.
In your shoes
Sand is fine and finds the way through every tiny gap and crack, even where we dislike it. Sand by science meaning measures 0.06 - 2 mm / 42 ga - 12 ga. Smaller particles are by definition called mud, bigger particles are gravel. See sandology
Glass, pottery, casting molds, filter, concrete, streets and many other man made things would be unthinkable or impossible without sand.
... and of course in Sandpictures
Domesticated sand with the mission of generating calm, relaxation and peace.