Soil composed of which type of clays, are best suited for agriculture?

Generally, soil contains 40 - 45 % inorganic matter, 5% organic matter, 25% water and 25% air. To sustain plant life, the proper mix of air, water, minerals and organic material is required.
Normally for agriculture purposes, Loamy-textured soils with equal distribution of sand, silt and clay are considered best.
However, the clay soils have great potential and are very fertile specifically with the presence of Chlorite and Illite.