That's pretty dense rock and really expensive for how much there actually is. I've seen them before..aren't they something like 3-4ish lbs...and it's $12? That's such a scam! I'd suggest seeing if your lfs
has any base rock (if you have one near). Craigslist is great too, and maybe you could get some rubble or rocks from BRS w/ an order of equipment too..?