Fracture
Uneven, Conchoidal, Brittle, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
  
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
  
Chemical Composition
Na(Li 1.5Al 1.5)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012) More from other references
  
Ca 3Fe 2(SiO 4) 3Arthur Thomas , Gemstones (2009)