绿柱石（Beryl），又称为“绿宝石”，化学式为Be₃Al₂(SiO₃)₆，其中含有氧化铍（BeO）14.1%，氧化铝（Al₂O₃）19%，氧化硅（SiO₂）66.9%。六方晶系，晶体呈六方柱形，柱面有纵纹，晶体可能非常小，但也可能长达几米。硬度为7.5-8，比重为2.63-2.80。纯净的绿柱石是无色的，甚至可以是透明的。但大部分为绿色，也有浅蓝色、黄色、白色和玫瑰色的，有玻璃光泽。英语绿柱石（Beryl）一词来源于希腊语“海水般的蓝绿色”（beryllos）。

In geology, beryl is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be₃Al₂(Si O₃)₆. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white.