What kind of matter is sand?

Sand:

1. Individual grains of sand are solid.
2. Sands are solid materials though they are tiny granules.
3. When these are combined, it seems fluid.
4. Example: falling sand dunes, avalanches, etc.
5. When it keeps in a container, sand retains its container's shape.
6. It is solid because each grain of sand has its own shape.
7. They retain this shape.