Berilo

Beryl is a beryllium aluminium cyclosilicate that crystallises in the hexagonal system and shows vitreous lustre, with colour varieties such as aquamarine, blue from Fe2+, and a green variety coloured by traces of chromium and vanadium.

Within its crystal framework, traces of iron (Fe2+) produce blue aquamarine by partial substitution of aluminium. A green variety is coloured by traces of chromium and vanadium. Transparency and vitreous lustre are characteristic.

It forms in granitic pegmatites, commonly associated with micas, feldspars and quartz. Associations with muscovite in prismatic aggregates are typical of Brazilian granitic pegmatites. It commonly develops long, striated hexagonal prisms. In aquamarine the hues range from icy blue to blue-green. In gemmology, aquamarine of pure blue without a greenish tint is preferred.

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