@elizabethtasker (whenever I hear the term "gunk" I always think of refractory highly colored organics you find on outer solar system comets and worlds: "Tholins" "tholin gunk" "organic gunk". I'm not sure how much there would be on Phobos, probably a little, but is it enough to make a big difference in properties?)

((I've definitely been in meetings and conferences where "tholin gunk" + shrug of shoulders is because nobody knows what the actual chemical structures are.))

@elizabethtasker The wierdness of Titan challenged all these definitions. I use a combo of composition+size descriptor.

For example, "silicate sands" on Earth, but also "gypsum sands" (like White Sands, New Mexico).

On Titan, mostly "organic sands". But there are also rare patches of "water ice sands", too.

Size-sorting is done by wind (Earth, Mars, Titan) and liquid (water for Earth and Mars, methane-nitrogen for Titan).

But without sorting (impact stuff), maybe "rock particles" would work?