Another option for mail-order gem gravel that I was pleased with was Gem Mountain Sapphire Mine. What a thrill it is to find sapphires! Some of the finds were large, 6 carats or more! I ordered 9 of the $45 gravel buckets (you get a bag in a flat rate Priority mail box, bucket not included). Their gravel ordering page is here: https://gemmountainmt.com/product-category/gravel 
Our postmaster was less than thrilled with our purchase when it came in and motioned us to pull around back to meet a cart full of dirty boxes full of gravel. Totally worth it, I spent hours pouring over this material pulling out hundreds of sapphires in every color.
Now, what to do with these lovelies? If I'd had my faceting machine then, I would have cut them myself, but I didn't. So I sent my largest pieces back to Gem Mountain for evaluation, heat-treating and faceting. A little while later, I got a phone call telling me about the stones and what they recommended I do with them. I opted to have the facet-able ones heat treated and sent off to Sri Lanka for faceting. They returned the flawed stones to me right away, but because of the wildfire smoke in the area (Montana) the heat treat wait was about 6 months, plus time to get faceted. I expected to wait a year to get my finished stones, but was surprised when they called to reconfirm my address and sent my sapphires early.
The whole process from first gravel order to faceted stones in hand took me 10 months and cost $600 including gravel, faceting and heat treating. I ended up with 6 beautiful faceted sapphires, the largest being a 1.5 carat yellow/blue bi-color and hundreds of rough sapphires to use in jewelry.
