Abstract

A chemical analysis of hambergite [Be2(OH, F)(BO3)] from the Little Three mine, near Ramona, San Diego County, California, disclosed that the mineral from this locality contains 6.0 per cent fluorine. Hambergite from a second California locality, the Himalaya mine near Mesa Grande, contains 0.2 per cent fluorine. Fluorine was not reported in analyses in the literature of hambergite from Madagascar, Norway, and Kashmir. New analyses of Madagascar and Norway hambergite gave 1.0 and 0.15 per cent fluorine, respectively. No material from Kashmir was available for study.

New data on hambergite from Anjanabanoana, Madagascar, and the Little Three mine, California, follow: Madagascar—BeO 53.6, B2O336.O, H2O 8.8, F 1.0, less O = F 0.4, sum 99.0 per cent; orthorhombic, a = 9.76 ± 0.01, b= 12.23 ± 0.01, c = 4.43 ± 0.01 Å. California—BeO 52.9, B2O3 36.6, H2O 6.7, F 6.0, O = F 2.5, sum 99.4 per cent; orthorhombic, a = 9.78 ± 0.01, b= 12.40 ± 0.01, c = 4.47 ± 0.01 Å density 2.372 (obs.) gms/cm3; α=1.543, β=1.580, γ= 1.617 ± 0.001, 2V = 90°. Crystals from the Little Three mine show two new forms, {1340} and {341}.

Substitution of F for OH in the Little Three material has caused the unit cell to expand in the b and c directions, while a remains essentially the same. This is because some hydrogen bonds lying in the bc plane are broken by replacing OH with F. Substitution of F for OH in the Little Three material has also substantially lowered the refractive indices and increased the density.

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