Very cool,
Rick.
Nice find. I've been to 2 of the local stores, and they don't carry anything like that. This stuff, depending on its looks could completely be used for DSB

We are sort of close - what store did you get that at? A chain store hopefully.
"Ol' Skool+", eh?
1 cement, 1 sand, 1.5 CO, 0.5 CC and 1 salt. Feel free to alter this somewhat - "Ol' Skool" to my mind isn't an exact recipe, but the combination of materials - typically Sand, Crushed Oyster Shell and Crushed Coral. So long as you keep the ratio around 3-5 parts "other" (and the salt counts as other) to 1 part cement, you should feel free to find what makes you happiest rock-wise.
Just be sure to tell us what it was
Dry blend all materials, except salt. I mostly just use my hands, in heavy rubber gloves, and I prefer to mix in a rubbermaid storage container (the really flexible, non-see though type) - I like the right angles, and you can thump them around without breaking them.
Add water, just a bit at a time, and when it starts to get close, just a splash at a time - two tablespoons can be too much at the "getting close point". Once you are satisfied that you have a pretty moist, but not wet mud, add the salt in and gently "toss" it in to blend. Don't overwork it - it shouldn't take more then 15 seconds to mix the salt in.
Wet your casting sand. Again, I like rubbermaids to cast in - the lids keep moisture in, and allow me to reuse the sand over and over. Make whatever shapes you fancy and can manage (I wish I was good at branchy stuff, but can't get the hang of it

), cover completely with wet sand and sort of smooth it in. At this point, you can sort of work your fingers into the mass you have made and give it some randomness, and poke it with a bit of wire. Lacing bits of sand through the structure, as you cast will add porosity and crannies for bugs to live in. Make a ball of sand and place it on a splat of mud and cover almost completely, to make a cave.
Have fun with it.
You did get the form, I sent, correct? If not, PM and I will send again.
Let us know how it goes.
Good Luck!