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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) Related PostsJasper gemstone Sapphire as talisman Healing stones 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 [...] Color is one of the most wonderful effects in nature. It is an attribute of light and is not a part of the object which appears to be coloured; though all objects, by their chemical or physical composition, determine the number and variety of vibrations passed on or returned to the eye, thus fixing their [...] What constitutes a precious stone is the question which, at the onset, rises in the mind, and this question, simple as it seems, is one by no means easy to answer, since what may be considered precious at one time, may cease to be so at another. There are, however, certain minerals which possess distinctive [...] |
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