After being ejected out of a volcano, grey cinder/volcanic rock gets its appearance from the simultaneous rapid cooling and depressurization process. Grey Cinder Sand has small cysts, which is what causes it to be so light in weight. We crush it down to make 138 CSX SP Wabash Grey Ballast.
This product is manufactured with HO to dust as a special effects ballast. Railroads use what we call sand and gravel used around the railroad to fillin low spots. Application: Spread the material right out of the package. Wet it down with water that has a few drops of soap added to it. Bond it with diluted white glue and water.