Garnets may, moreover, figure under another name quite unintentionally. Probably many a fine stone masquerades as a true ruby; the impossibility of distinguishing these two species in certain cases by eye alone is perhaps not widely recognized. An instructive instance came under the writer’s notice a few years ago. A lady one day had the misfortune to fracture one of the stones in a ruby ring that had been in the possession of her family for upwards of a century, and was originally purchased of a leading firm of jewellers in London. She took the ring to her jeweller, and asked him to have the stone replaced by another ruby. A day or two later he sent word that it was scarcely worth while to put a ruby in because the stones in the ring were paste. Naturally distressed at such an opinion of a ring which had always been held in great esteem by her family, the lady consulted a friend, who suggested showing it to the writer. A glance was sufficient to prove that if the ring had been in use so long the stones could not possibly be paste on account of the excellent state of their polish, but a test with the refractometer showed that the stones were really almandine-garnets, which so often closely resemble the true ruby in appearance. Beautiful as the stones were, the ring was probably not worth one-tenth what the value would have been had the stones been rubies. To the student of mineralogy garnet is for many reasons of peculiar interest. It affords an excellent illustration of the facility which certain elements possess for replacing one another without any great disturbance of the crystalline form. Despite their apparent complexity in composition all garnets conform to the same type of formula: lime, magnesia, and ferrous and manganese oxides, and again alumina and ferric and chromic oxides may replace each other in any proportion, iron being present in two states of oxidation, and it would be rare to find a stone which agrees in composition exactly with any of the different varieties of garnet given below. [Illustration: FIGS. 75, 76.—Garnet Crystals.]