Black Lava Rock ,Average Size Stones 1/4" to 1/2" (6 Quarts) MIGHTY 109 1/4 inch average size of stones. 6 quarts per bag. Great as a ground cover or for garden paths and planter beds Bold black and gray color tones. Helps to maintain moisture, aerate soil, prevent erosion, and improve drainage. Course and porous stone. Very light weight.