Since most precious stones are small in size, in order to better observe the imperfections such as inclusions and fractures on the gemstones, microscopes and magnifying glasses are employed. A microscope with 10X or 20X magnifications is usually used to observe the gemstones; for more detailed observations, magnification up to 70X can be used. Aside from observing inclusions and fractures, these instruments can be used to observe the cleavage planes, growth lines, color bandings, surface graining, and the degree of external polishing. Sometimes they can also identify layers of assembled stones.