Scientific American Supplement, No. 1082, September 26, 1896
Scientific American Supplement, No. 1082, September 26, 1896
Various
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| Idocrase. | Peridote. \ Axinite. 7. Quartz. / Quartz. | Tourmaline. | Cordierite. \ Garnet. / Andalusite. | Zircon. | Emerald. \ Phenacite. 8. Topaz. / Spinel. | Topaz. \ Chrysoberyl. 9. Corundum. / Ruby. \ Sapphire. 10. Diamond. Diamond. Among precious stones diamond stands out pre-eminent as the hardest ofall known substances. Ruby and sapphire are scratched by diamondalone, while chrysoberyl, topaz and spinel scratch all the remainingstones, although they do themselves yield to the scratch... of ruby andsapphire. The hardness is a character still generally utilized by theexpert when he is in doubt; in experienced hands it has some value. Bylong practice it is possible to form a very close estimate of thehardness of a given stone, and that often, not by the scratch of theother minerals in the scale, but by the feel of the stone against afile; the resistance offered by the stone to the file is taken as ameasure of its hardness. It is not a character capable of any accuratemeasurement, neither is it to be recommended for use by inexperiencedpersons.
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