After the first few minutes measure depth of your sand layer. Sand is very light in color, drains fast and is easy to work in. Its draw back is that is not a fertile medium. In four or five hours the silt will settle, the color and texture is distinct. The color is a medium to dark brown and it has some fiber in it.
Silt holds moisture reasonably well, it is fertile.
However it can compact easily, so be careful not to walk or run heavy equipment over it. At the end of the 24 hours you will have the clay layer. Clay is very slow to drain, high in nutrients, the color has a warmth to it. From the layering you can make a guess on the percentage of sand, silt, and clay from the depth of each layer. Sand is large and blocky, it does not compact.