Unusual Rock Formation

This is a collection of unusual structures on the underside of a small sandstone overhang. It’s made of different material than the surrounding sandstone, it’s a hard to the touch with no visible sand grains. Most of the surface is made of tiny nodules that almost look like condensation on a cold surface. In the center is a more prominent raised area that looks like a cast of an animal burrow.

Unusual formation in a sandstone overhang. Looks like a cast of an animal burrow. Camera cap for scale

It’s located at the base of a gully near a creek, it looks like it goes through wetting and drying cycles as rain runoff flows and drys. I wonder if it  could be the slow build up of minerals that are carried in the water then are deposited as it drys out.

Wider view of the same area. The surrounding nodules are visible. The wet overhanging sandstone can be seen at the top left.

• Rock
• Sandstone