Difference between clay and sand soil

Sand
Sand is a very basic soil, made of particles of rock and hard minerals, such as silicon dioxide. The largest of the different types of soil particles, one grain of sand is visible to the naked eye. According to a comparison made by Penn State Extension, if a particle of clay were a BB, a grain of sand would be the size of a chair. Although sand supports very few plant life forms in comparison with other soil types, sand is a valuable component of an optimal soil mixture. The large, relatively stable sand-particle size increases soil aeration, improves drainage in tight soils and creates plant-growth supporting qualities, or tilth.

Clay
Clay is the tiniest soil particle. Compared to sand particles, which are generally round, clay particles are thin, flat and covered with tiny plates. Clay particles tend to stick together and make very little movement through soil. Negatively charged, clay particles attract positively charged nutrients — such as potassium, calcium, magnesium and certain types of nitrogen, providing valuable nutrients to plants. Clay also tends to hold moisture, improving water retention qualities of soil but reducing drainage potential. The color of clay soil depends upon minerals attached to the particles and the amount of water in the soil. Yellow and red clay contain varying amounts of iron oxide and drain more freely than blue or gray clay soils. The colors blue and gray indicate the soil stays wet most of the year and very little iron, if any, is attached to the particles.