These blocks can be found in Canyon Biomes covering the surface of valleys between canyon-mounts. They can be taken (mined / pulled) even without having any Power Cells equipped.
Currently these blocks cannot be used in any crafting-recipes.
However if placed in a large enough amount together during daylight aggressive Dustevils and occasionally Trogs can spawn on these blocks, while at night Night Pigsies can appear.
As of May 2022, there is a glitch that pets and players sometimes fall through any blocks used as flooring to caverns below, which can occur all the way down to the corruption layer from the surface. There are a handful of reports that using canyon floor underneath another block prevents this glitch, but more tests are required.