Engine terminal "Asphalt"

You could use roofing paper as a base and pour high gloss black paint puddles.

Many of your craft stores (Michaels, Hobby Lobby) sell colored sand.  It tends to be shiny but, if you it with some matte finish, it might be what you are look for.

We used black, Fine Cinders from Woodland Scenics. Tamped them down very flat, then moistened them with cheap alcohol, then glued with slightly diluted Matt Medium.

Hot Water posted:

We used black, Fine Cinders from Woodland Scenics. Tamped them down very flat, then moistened them with cheap alcohol, then glued with slightly diluted Matt Medium.

and it looks great!

Great suggestions. If you are set on real sand, have seen Black sand for sale. Doubt the "dye" method would work good.

Sand, fine ballast combo then patches of india ink (if too dark, dilute with some isopropl alcohol). Experiment with it first on a separate surface to see how it changes the sand/ballast mix to your liking. You can dribble it on with a small brush or with an eye dropper and it will spread like oil stains. 

Got some fine sand and India Ink for experimentation.

Pure sand and sand mixed with gray/black roofing granules.

India Ink and Minwax black stain both reacted and spread similar.  Batches are in process of drying now.  Will the Ink or Stain act as a binder or I assume still need to be glue sprayed?  No doubt the stain is a whole lot cheaper.  The ink seemed to be a little glossier at least straight out of the bottle.

Saw a product from Elmer's called Washable Clear Glue (not School Glue).  Has anyone ever used this and with what results?  Seems to be just slightly thinner than white glue all.  Would assume a thinning similar to glue all with water and a little alcohol.  The clear is more expensive but if you don't have the possibility of residual talc , it may be worth it.

The sand was art sand from Hobby Lobby and is very fine and white.  Play sand from a hardware store should do OK for the "asphalt", the art sand will be used at the sand towers.

Thoughts?

Sounds like you're off to a good start. The India Ink will not act as a binder. So, you'll need to glue afterwards. I dilute the Elmer's 3:1 with water. Goes a long way. Have only used the Glue All and have no experience with the Washable Clear Glue. If you need a lot of it, you can buy a gallon on eBay for about $16-$20 or so. I douse with 1:1 water/alcohol mix, the apply the diluted glue. Have used it on track ballast and scenery and it holds down very well. If the India Ink is a bit pricey, you can also dilute with Iso Alcohol which will make a lot more of it without affecting the color much.