红宝石的化学成分为三氧化二铝（Al₂O₃），因含微量元素铬（Cr³⁺）而成红至淡红色。透明度为透明至半透明，并带有玻璃光泽。折射率为1.76-1.77，双折射率为0.008-0.010，硬度为 9，密度3.95-4.10克/立方厘米。天然红宝石大多来自亚洲(缅甸、泰国和斯里兰卡)、非洲和澳大利亚，美国蒙大拿州和南卡罗莱纳州。

The chemical composition of Ruby is Al₂O_3.The color is from red to light red due to trace elements of chromium (Cr^{3 +}). Transparence of Ruby is transparent to translucent, and has glass luster. Refractive index is 1.76-1.77, double index is 0.008-0.010.The hardness of Ruby is 9, density is 3.95-4.10 g/cm³. Natural Ruby is mostly from Asia (Myanmar, Thailand and Sri Lanka), Africa and Australia, and the Montana and South Carolina of USA.