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Sec. III, Ch. 1: The Ruby

Sec. III, Ch. 1: The Ruby Page of 366 Sec. III, Ch. 1: The Ruby Text size:minus plus Restore normal size   Mail page  Print this page
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The Ruby.
India. Corundum occurs in a great variety of conditions, some being coarse and opaque, while others are translucent or transparent, but it is only the latter which take rank as gem-stones, and can be used for jewellery.
All forms of Corundum are found by the chemists to contain more than half their weight of the metal, Alumin­ium. The oxide of this metal is called Alumina, and it is this substance which, in its natural state, forms the mineral Corundum. As a silicate, Alumina forms the basis of all clays, and a multitude of other common minerals and rocks ; while as a sulphate it enters into the composition of Alum —whence indeed the word " Alumina" is derived.
The coarse varieties of Corundum are more or less impure, but the transparent crystals exhibit the Alumina in a state of approximate purity—being uncontaminated with any other substance, save perhaps a trace of certain metallic oxides, on which the exquisite tints of the coloured Corundums depend, but which are present in such minute quantity as well-nigh to elude the vigilance of the chemist.
Those Corundums which present a red or reddish colour are the true Ruby—this stone being sometimes described in works on mineralogy as the Oriental Ruby, in order to distinguish it from such stones as the Spinel and others. The main fact to be borne in mind with respect to the distinctive character of the Ruby, from a mineralogist's point of view, is that it is really a variety of crystallized Alumina. It will be shewn in a subsequent part of this work that the Sapphire has practically the same chemical composition and the same physical char­acters, the difference between these stones being mainly one of colour. It is believed that the fine colour of the Burma Ruby is due to the presence of oxide of chromium, associated in very small proportion with the alumina.
Sec. III, Ch. 1: The Ruby Page of 366 Sec. III, Ch. 1: The Ruby
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