colloidal phosphate consists of clay particles surrounded by natural phosphate. Total phosphate is around 20% and "available" phosphate about 2-3%. An efficient use of colloidal phosphate is to add it directly to livestock manure in the barn or lot, where the manure acids dissolve much of the total phosphate and the phosphate stabilizes the nitrogen in the manure. Many of the same advantages can be had by adding 20-50 pounds of colloidal phosphate to one ton (two cubic yards) of manure when composting. The ATTRA publication Farm-scale Composting Resource List directs the reader to many useful resources on composting. When direct land application of rock phosphate is the only possibility, spreading rates between 500 and 2,000 pounds per acre are appropriate, depending on phosphorus status, soil acidity, and finances.
Above from here - http://attra.ncat.org/attra-pub/altsoilamend.html
Geologists classify it as a colloidal, montmorillite clay from an ancient ocean deposit, rich in sediments, minerals and sea life. This fossil clay from an ancient seafloor contains over 70 trace elements, and is touted to boost the growth and health of almost any plant.
above from this - http://www.championtrees.org/topsoil/EarthPlus.htm