Natural volcanic rock used as the primary long-term aeration amendment in BAS living soil. BAS uses a 3/8-by-1/4 grade (clean, without sand fines), sourced from New Mexico, food/beauty industry grade, heavy-metal tested. Unlike perlite, pumice does not float to the top and stays in the soil forever.
Jeremy shows the pumice in the mix and calls out it's 'real soil' — a rock, not obsidian popped like popcorn.