The most common crystal shape of beryl requires at least two crystal forms to form a complete crystal. The first is a hexagonal prism. The second is the basal pinacoid. The combination of these two forms gives the prismatic and tabular shapes with which we are so familiar. To date, over 65 different crystal forms have been identified on beryl crystals.
Size is a major factor concerning crystal complexity.
Most of the highly modified faces appear only on smaller crystals, growing out of existence as the crystal becomes larger. Crystal forms present are also affected by impurities. Alkali beryl such as morganite is often considerably more modified than aquamarine and heliodor whose principal faces are typically the basal pinacoid and first order prism. When a very small quantity of certain metallic ions are included in the crystal structure of beryl, color centers are created which provide the various hues for which beryl is noted. Depending on which impurities are present, crystals can range from blue to green to yellow to orange to red, virtually the entire spectrum.