Fracture
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Uneven
  
Uneven
  
Chemical Composition
Mn 3B 7O 13ClMichael OâDonoghue , Gems, Sixth Edition (2006)
  
(Mg,Fe2+ ) 5Al(Si 3Al)O 10(OH) 8Anthony et al , Handbook of mineralogy (2001)