re: What kind of sand for filling in lawn?

Lots of bad info in this thread. The correct answer is river sand. Builders sand is coarse and drains quickly. If you fill a small hole with builders sand and cover with sod, the sod will wilt constantly because the soil won't hold moisture. River sand is dense and holds moisture. Shapes and forms easily. It is used to grade every yard after construction.

To address weeds. Weeds are not found in sand. People believe this because after being spread the sand grows weeds. Sand is coming from deep pits dug several feet below. Little to no seeds down there. The weeds growing are from weed seeds that blow on to the soil, bed easily and grow due to the moisture present. Think of cracks in a driveway, seeds blow into a crack where dirt washed into. Boom, a weed.

LINK. River sand and torpedo grass

Where can one purchase river silt?

If it is a white clean sand I would definitely use it