Rock Dust Local's own "House Mix". A "90/10" blend of BrixBlend Basalt and St. George Black rock dust. This is a unique combination of the alkaline silicate basalt and a carbonaceous shale sediment containing organic carbon. The course "grits-to-dust" (1/8"-0) gradation is perfect for soil mixes or as an addition to garden soils and growing media. With the largest particles from the St. George Black and the finest from the BrixBlend Basalt, this mix is supremely suited for fruit and vegetable growing where a healthy dose of Calcium, Magnesium, Potassium, Sulfur and Carbon are needed. Use at 5-20 lbs./ 100 sq. ft. Ships in a 40 lb box.