Our walmart has bags of stones in the craft section. They're cheap too.
Debbie - Virginia Debbie
is saving pizza boxes for her molds/forms. I'm betting you could go to a local pizzeria and they would sell you as many boxes as you need for cheap. Course 4 pieces of lumber works as well and you can keep re-using the forms.
Be sure to throw some mesh/re-rod/any old pieces of metal you may have into the concrete before it sets up. You want the metal 40% from the bottom.
I don't know how many stepping stones you're making but if it's more than a dozen, it would be cheaper to go to your local brick and block place and buy bag(s) of Portland Cement and then go the to gravel place and have them dump 3/4 mix into the bed of your truck. The mix would be 5 to 1 with 5 being the 3/4 mix.
If the stones or glass don't pan out, pebbles on top look really well too. I love the look of exposed aggregate.
http://www.google.com/search?q...
We had exposed aggregate knee walls along our walks in OH. Loved the look of it.
Can't WAIT to see the finished product