3.346 " 3.410
Olivine 3.334 " 3.368
Chrysolite 3.316 " 3.528
Jade 3.300 " 3.381
Jadeite 3.299
Axinite 3.295
Dioptase 3.289
Diopside 2.279
Tourmaline (yellow) 3.210
Andalusite 3.204
Apatite 3.190
Tourmaline (Blue and
Violet) 3.160
Tourmaline (Green) 3.148
" (Red) 3.100
Spodumene 3.130 and occasionally to 3.200
Euclase 3.090
Fluorspar 3.031 and occasionally to 3.200
Tourmaline (Colourless) 3.029
Tourmaline (Blush
Rose) 3.024
Tourmaline (Black) 3.024 and occasionally to 3.300
Nephrite 3.019

_Group_ E.--Stones whose specific gravity lies between 2.50 and under
3.000.

Phenakite 2.965
Turquoise 2.800
Beryl 2.709 and occasionally to 2.81
Aquamarine 2.701 " 2.80
Labradorite 2.700
Emerald 2.690
Quartz 2.670
Chrysoprase 2.670
Jasper 2.668
Amethyst 2.661
Hornstone 2.658
Citrine 2.658
Cordierite 2.641
Agate 2.610
Chalcedony 2.598 and occasionally to 2.610
Adularia 2.567
Rock-crystal 2.521 and occasionally to 2.795

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

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

_Group_ G.--Stones whose specific gravity is under 2.00.

Jet 1.348
Amber 1.000

(See also list of stones, arranged in their respective colours,
in Chapter XII.)

In many of these cases the specific gravity varies from .11 to .20, but
the above are the average figures obtained from a number of samples
specially and separately weighed. In some instances this difference may
cause a slight overlapping of the groups, as in group C, where the
chrysoberyl may weigh from 3.689 to 3.752, thus bringing the heavier
varieties of the stone into group B, but in all cases where overlapping
occurs, the colour, form, and the self-evident character of the stone
are in themselves sufficient for classification, the specific gravity
proving genui