TOURMALINE

CLASS: Cyclosilicate. . . CHEMICAL FORMULA: (Na, Ca) (Al, Fe, Li) (Al, Mg, Mn) 6 (BO3) 3 (Si6O18) (OH, F) 4. . . CRYSTAL SYSTEM: trigonal
CRYSTAL FORM: prisms, often elongated, vertically striated
COLOR: colorless, blue, black, brown, pink, red, green
PHYSICAL PROPERTIES: very hard (7/7,5 Mohs), heavy (3/3,25 g/cm3), lack of cleavage, transparent / translucent, vitreous gloss tending to resinous at fracture points, pyroelectric, very piezoelectric, insoluble in acids and birefringent (double refraction).
CURIOSITIES: related to healing properties, transforming negative energies into positive ones.