Phosphates & Oxides
Oxide
What it is
A broad category of minerals where metals bond directly with oxygen. This includes the rare and brilliant chrysoberyl, whose variety alexandrite is one of the most valuable gemstones — changing from green in daylight to red under incandescent light.
How it forms
Oxides form across many environments. Simple oxides like corundum (Al₂O₃) form in silica-poor igneous rocks. Complex oxides form in pegmatites and metamorphic rocks.
Metal + Oxygen (various ratios)
