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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 [...] The fixing of the specific gravity of a stone also determines its group position with regard to weight; its colour and other characteristics defining the actual stone. This is a safe and very common method of proving a stone, since its specific gravity does not vary more than a point or so in different [...] |
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