Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006), Uneven
111 (perfect in four directions)
From the Greek, oligos and kasein, little cleavage.
C
Na(90-70%)Ca(10-30%)(Al,Si)AlSi 2O 8Michael OâDonoghue , Gems, Sixth Edition (2006)