Clavius question

[frenat]

On this page
www.clavius.org/gravdust.html
in the second answer, it says
"This scenario doesn't produce all the effects of lunar soil that can be simultaneously observed in the videos: dryness, dustlessness, and imprintability. Sand will not hold a footprint unless it is wet, and if it is wet it will land in clumps after being disturbed. If it is dry, but the particles are small enough to hold a print, it will form dust clouds in air when disturbed. "
The way I read the last sentence I don't think it would be sand anymore, at least I've never seen any dry sand hold any print. The sugar white sands on the beaches around Panama City here (bragging just a bit ;D) seem very fine grained and definitely don't hold a print. Is that last sentence intended for it to still be sand, or some other kind of dusty soil? Is there a kind of sand that is that fine grained enough to hold an imprint when dry?

[echnaton]

The grains of beach sand is rounded while bank sand tends to be more jagged and will hold a better print. Bank sand is used in construction because the sharp edges make it resistant to washing away.

Enjoy those beaches while you can. I hope the oil stays away.

[frenat]

The sentence in question doesn't distinguish between rounded or jagged but simply particle size.

[JayUtah]

You know, that's just a badly-written paragraph. There are indeed two variables -- particle size and particle complexity -- that bear on whether a particulate is impressible at some scale. We tend to think of sand as large, round grains. Small round grains have a fundamentally similar angle of repose, so that would explain why the fine-grained sand doesn't really improve the impressibility. You have to go to a larger scale impression. The complexity determines the matrixing potential, which is why jagged sand of any scale can be useful. The point I think I was trying to make is that once you get a small enough particulate to be impressible at the scale of a footprint, you have to deal with aerosolization.

[frenat]

That's what I figured. It came up on another site with DavidC/Rocky.