Mineral
Probertita
NaCa(B₅O₉)·5H₂O · Boratos
Probertite is a rare hydrated sodium–calcium borate, first described in 1883 in California. It usually occurs as prismatic, colourless to white crystals; most known specimens from California—its type locality—and Turkey form dense aggregates of elongated prisms, ranging from translucent to opaque. Specimens from Kohnstein stand out for the opposite: transparent, cleaner crystals that are visually much finer.
Etymology
Named after Frank H. Probert (1850–1920), an American chemist.