If it’s blue and bladed, it’s kyanite. Sometimes also if it’s white and bladed, or gray and bladed.
Kyanite is a polymorph of andalusite and sillimanite. These three minerals share the same formula, but are stable at different P/T conditions.
Physical Properties |
|
| Chemical formula | Al2SiO5 |
| Class | Nesosilicate Isolated tetrahedra |
| Crystal system | Triclinic |
| Habit | Bladed Tabular Parallel or radiating aggregates |
| Color | Blue to white |
| Hardness | 5 to 7 |
| Specific gravity | 3.6 |
| Cleavage | Two prominent: Perfect (100), good (010) |
| Fracture | Uneven |
| Luster | Vitreous Pearly |
| Transparency | Transparent to translucent |
| Streak | White |
Optical Properties |
|
| PPL | Typically colorless May be weakly blue and pleochroic High relief |
| XPL | High relief 1st order interference colors |
| δ | 0.016 |
| after Perkins, 344-345 |
Kyanite in Hand Sample
Kyanite
Blue kyanite speckled with garnet and chalcopyrite
Kyanite quartzite
Scanning electron micrograph of kyanite
Kyanite in Thin Section
Thin Section GigaPans
Kyanite quartzite, plane polars
Kyanite quartzite, crossed polars
Kyanite, Plane Polars
Kyanite in quartzite, in plane polarized light. To view this mineral in crossed polars, click here: https://youtu.be/H4jcL7exIOI To explore this slide in pla…
Kyanite, Crossed Polars
Kyanite in quartzite, in plane polarized light. To view this mineral in plane polars, click here: https://youtu.be/aOsD_lRYWuc To explore this slide in plane polars, click here: https://viewer.gigamacro.com/view/xTYqmupFt7lI7nYw To explore a gigapan of this slide in crossed polars, click here: https://viewer.gigamacro.com/view/6TgFi0nJaqEdFjVD To explore a gigapan of a hand sample of kyanite, click here: https://viewer.gigamacro.com/view/UnbzlZe7tNYmjGLK NVCC slide AN 86.