Check out sand blasting sand. You can get a variety of diameters and colors from a store that specializes or supplies to stores.
Black diamond is coal slag but used widely, and I use Garnet sand actually made out of Garnets and can be purple pink to amber sunset color depending un where it is mined.
Sand blasting sand is generally cleaner than construction sand too. Around 40-50 lbs for ~$18-25.