Goshenite , the colorless variety of beryl, is often used as a replacement for more valuable colorless gems. Goshenite may also be coated with a green foil to resemble emerald , as its physical properties are identical to emerald. Green beryl , the light green variety of beryl, should not be mistaken for emerald , which occurs in a much darker green. Green beryl is usually heat-treated to form deeply colored aquamarines . Bixbite is a strawberry-red variety of morganite, with a brownish hue.
Red beryl is a rare, deep red variety found in only one place in the world.
Blue beryl is a dark blue variety, synthetically colored by irradiating light blue aquamarine. Most of these variety names are universally used, but some, such as bixbite and blue beryl are not well-known. Internal flaws in beryl gems can be masked by treating the stone with oil. Unscrupulous dealers will often apply this treatment to a stone without informing the buyer. All the varieties are faceted into various gem cuts, and some stones display asterism and cat's eye effect when cut and polished into cabochons .