Silicates & Quartz
Kyanite
What it is
A remarkable mineral with two different hardnesses depending on which direction you scratch it. Blue kyanite forms blade-shaped crystals, while black kyanite forms fan-shaped sprays. Both are aluminum silicates that only form under high pressure.
How it forms
Forms exclusively in high-pressure metamorphic rocks like schist and gneiss. Kyanite is an indicator mineral — its presence tells geologists that the rock experienced extreme burial depth.
Al₂SiO₅ (Triclinic)
