CLASS: Nesosilicate. . . CHEMICAL FORMULA: Al2OSiO4. . . CRYSTAL SYSTEM: Triclinic
CRYSTAL FORM: pinacoid, elongated tabular crystals
COLOR: blue, white, grey, green.
PHYSICAL PROPERTIES: very hard (7 Mohs) perpendicular to the long side and medium hard in parallel direction (5 Mohs), heavy (3,67 g/cm3), fragile, perfectly exfoliable, transparent/translucent, vitreous/pearly luster, infusible, unassailable by acids.
It is also known as DISTHENE, in relation to its double hardness. The word comes from the Greek.
CURIOSITIES: it is related to relaxation and to the contribution of calmness.