Beryl is a beryllium aluminium silicate (Be₃Al₂Si₆O₁₈). It is a very hard mineral (its hardness is 8 on the Mohs grade 10 scale) and usually forms columnar crystals. Its beautiful, colourful, transparent versions are popular gemstones, some colour variations even have separate names; the best known of these are the green emerald and the navy aquamarine, but the colourless goshenite, the yellow heliodor, and the pink morganite are also worth mentioning. In the region of Voineasa in the Carpathians, huge crystals of up to 10 cm are known, but they do not come close to the quality of a gemstone; they form white or light grey, opaque crystals, thus they are not used to make jewellery.
In the picture: Beryl, Voineasa, Romania. Size: 11 cm. Photo by Géza Kulcsár