Hauynite to Opal

Group F. -Stones whose specific gravity lies between 2.00 and under 2.50.

Hauynite 2.470 and occasionally to 2.491
Lapis lazuli 2.461
Moldavite 2.354
Opal 2.160 and according to variety to 2.283
Opal (Fire Opal) 2.210 (average)