Crystal system:                 Hexagonal                                           Hardness:            6,5 – 7,5
Density:                               3,28 – 3,31                                           Streak:                  White
Colour:                                 Colourless, white, yellowish, pale to dark blue
Cleavage:                            None
Occurrence:                       A rare late hydrothermal mineral formed in granitic pegmatites.
Habitat:           ...

Continue reading ...