The hellandite group includes: hellandite-(Ce): (Ca,REE)4Ce2Al☐2(B4Si4O22)(OH)2 hellandite-(Y): (Ca,REE)4Y2Al☐2(B4Si4O22)(OH)2 tadzhikite-(Ce): Ca4Ce2Ti◻(B4Si4O22)(OH)2 Back to Minerals