Beryls

Beryl is a mineral species with the chemical formula Be3Al2Si6O18, a beryllium aluminium silicate. It crystallizes in the hexagonal system and commonly forms elongated prismatic crystals with a vitreous surface. On the Mohs scale it rates 7.5 to 8 in hardness, and it has a refractive index of about 1.57 to 1.60 with weak birefringence. The color of beryl ranges from colorless to blue, green, yellow, orange, pink, and red, depending on trace impurities.

Natural varieties are named for their color. Goshenite denotes colorless beryl; emerald is the well-known green variety caused by chromium and/or vanadium; aquamarine is blue to blue-green due to iron; morganite is pink from manganese; heliodor is yellow to golden from iron; red beryl, also called bixbite, is a rare red form. Each variety shares the same underlying mineral structure but differs in trace-element content that influences color.

Beryl forms in granitic pegmatites and hydrothermal veins, and it can occur in associated rock types such as quartz, feldspar, muscovite, and tourmaline. Economically important deposits have been found in Brazil, Colombia, and parts of Africa and Russia for emerald and aquamarine, as well as Utah and other locales for red beryl. Beyond gemstones, beryl is a principal source of beryllium, a metal used in alloys and specialized applications, which gives the mineral additional industrial significance.

Some gemstone beryls receive treatments to improve clarity or color, particularly emeralds, which are often oiled or fracture-filled. Synthetic beryl varieties exist and are used as alternatives to natural stones in jewelry.