金云母（Phlogopite），晶体属单斜或三方晶系的层状硅酸盐矿物，化学式为KMg₃AlSi₃O₁₀(F,OH)₂。金云母是白云母类矿物中的一种，它是含铁、镁和钾的一种铝硅酸盐。金云母成分中的铁如果不算多的话，它就可以作为电绝缘材料，因而有着重要的作用。

Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.

Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg₃AlSi₃O₁₀(F,OH)₂. Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content. For physical and optical identification, it shares most of the characteristic properties of biotite.