👉 Monoclinian is a type of mineralogy that describes minerals with two crystallographic planes that are perpendicular to each other. These planes are called the principal planes, and they are usually defined by their angle between them. Monoclinic minerals are characterized by their high refractive index at the critical angle (a value close to 90 degrees) and their low refractive index at a lower angle. Monoclinic minerals often have a wide variety of colors and patterns due to
