Bavenite has been identified from a gem tourmaline mine at Mesa Grande, California. This is the second recorded occurrence of this mineral, previously described from Baveno, Italy. Bavenite is a beryllium mineral, with about 3 per cent of BeO. The Italian bavenite also contains beryllium, not previously recognized. Three new crystal forms are determined; the optical properties are given, correcting an error in the optical orientation as published; and the chemical analysis leads to the formula 9SiO2 · A12O3 · BeO. 4CaO · H2O, with some uncertainty as to the exact ratio of the SiO2 and H2O. The California occurrence is a new pseudomorph after beryl.