I am looking to make fake soil. I would like the end result to look as close as possible to real soil, but be made up of solid parts that do not create goo, dust or other residue. I have tried coffee with glue but it is not solid enough. What should I use for this?
I've seen (dyed) crumbs of cork used as fake soil. You'd probably need to mix it with glue (diluted PVA perhaps) then sprinkle a last layer on top and dust off any excess, to hide the glue.
"Granulated cork" looks like a good search term. It's available in a range of particl sizes, so you could use the fine stuff for scale models, and something coarser if it should look life-size.