Get it as soon as Thu, Aug 19. FREE Shipping on orders over $25 shipped by Amazon. Lava Rock, Soil Aggregate for Bonsai, Cactus, Succulents, and Other Container Grown Plants, enables Optimal Drainage, Improves Soil Aeration 1/4 inch Black Lava Rock (2 Quarts Bag) 4.8 out of 5 stars. 360. $15.85.