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Group D. -Stones whose specific gravity lies between 3 and under 3.50. Rhodonite 3.413 and occasionally to 3.617 Garnets 3.400 ” 4.500 Epidote 3.360 ” 3.480 Sphene 3.348 and occasionally to 3.420 Idocrase 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 [...] 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 [...] Though the origin, formation, composition, characteristics and tests of each stone will be examined in detail when dealing with the stones seriatim, it is necessary to enquire into those particulars of origin which are common to all, in order thoroughly to understand why they differ from other non-metallic and metallic minerals. At the very commencement [...] |
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