Beryllium, caesium, niobium (columbium), germanium, hafnium, the rare earths,tantalum, titanium, yttrium, and zirconium
Résumé
Although considerably richer in BeO, bertrandite, phenaoite, chrysoberyl,barylite and other beryllium minerals have not so far played a large part in the beryllium-mining industry. Their crystal structure, generally very fine, makes them unsuitable for cobbing. Their low concentration in the metalliferous matrices in which they occur make them low-grade ores, difficult to locate, the working of which presents very difficult problems. Hone the less, these ores have a great future before them, and it can be assumed that they will soon take the place of beryl.