“A superb specimen of blocky {100} twin of pitch black aegirine from Mt Malosa. The twin boundary runs across the termination forming an obtuse roof and continues as a thin line down the {010} prism plane. (010) faces are rarely present on single crystals but very prominent on the (100) twins. Smaller crystals at the back side of the specimen are untwinned aegirines. Specimen size 5 cm. ”