- Color: green, yellow-green, brown, blue-green
- Hardness: 7
- Refractive index: 1.66 - 1.69
- Density: 3.25 - 3.35
- Chemical composition: (Mg,Fe)4(Al,Fe)6(SiO4,BO4)5(O,OH)2
- Crystal structure: orthorhombic
- Origins: Greenland, Tanzania, Madagascar, Kenya, Sri Lanka, Burma, Australia.
Collector's stone. Crystals demonstrate noticeable pleochroism effect, from yellowish-green to reddish-brown, with clean specimens over 5 ct. being rare.