Explanation

Emerald is the green variety of beryl, whose formula Be3Al2(SiO3)6 contains beryllium — indeed the mineral beryl is a beryllium aluminium silicate. Topaz is an aluminium silicate with no beryllium, while ruby and blue sapphire are both varieties of corundum (aluminium oxide). The green colour of emerald comes from trace chromium or vanadium. Hence emerald is the beryllium-bearing gemstone.