I live in Melbourne Beach FL and have spent most of the day searching for large bags of coarse horticultural vermiculite for my new square foot garden. Home Depot and Lowes doesn't carry it. Rockledge Gardens only has medium grade. I don't want to buy from a building supply store because I fear it might be contaminated. I gave up and came home and now I'm trying to find some online but many listings don't say whether it's coarse and many don't list the bag size in cubic feet. All of them seem to charge nearly as much (or more!) for shipping than for the product. Can anyone help me with my search?