THE RUBY, SAPPHIRE, ORIENTAL TOPAZ, etc
ALL the above stones are properly corundums, being identical in every particular but that of colour, which difference may be said to be the only cause of a change in the name· The red sapphire is a ruby, the blue ruby a sapphire, the yellow a topaz, etc. The name corundum itself is of Indian origin, derived from the Sanskrit korund, and is applied only to the opaque massive varieties, which, however, present the characteristic hexagonal crystal, and are generally of a dull colour.
The first European to class all the varieties of this gem under their proper names was Count Bournon, in the year 1802. The Eastern nations had, however, for several centuries adopted this classification.
A coarse variety of corundum is called emery, and is largely used for polishing metals, gems, marbles, etc. The principal source of this material is the island of Naxos, although it is found in Cornwall, Spain, Italy, and Asia Minor.
In the States of New York and New Jersey, red and blue corundum is found in crystals, in a matrix of micaceous limestone, accompanied by black spinels and other gems ; these crystals are perfectly opaque, and although of a fine colour cannot be used for jewellery. They are of small size, seldom exceeding an inch in length.
The first and more important variety is the Ruby, or red sapphire, which is the most valuable of all gems when of large size, good colour, and free from flaws,—exceeding even the diamond itself in value.
The specific gravity is 3*9 to 4· 1 ; its hardness is superior to any known substance except the diamond, being numbered 9 in Mohs’s scale. It is susceptible of electricity by friction, and retains it for a considerable time. ‘As will be seen, it is composed of alumina, and coloured by traces of metallic oxides, chrome, etc. :—
The various analyses prove that it does not contain silica, as has sometimes been erroneously stated.
The ruby as well as all other corundums is infusible alone, but in combination with a flux melts with difficulty into a clear glass. It is possessed of double refraction, although not to a very high degree. According to mineralogists, the system of crystallization to which all these stones belong is rhombohedral. The cleavage is basal, or in other words, the crystal breaks across the prisms with nearly a flat surface.
The lustre is vitreous. Occasionally specimens are found asteriated, or possessed of a star in the direction of the axis, the points of which terminate at the flat plane of the hexagonal prism, in a section across it. Rubies are found associated with sapphires, zircons, spinels, oxide of tin, magnetic iron, rutile, topaz, etc., sometimes in perfect crystals but slightly abraded, taper at each end; often the crystal exhibits various colours, in section across the prism, perhaps blue at both ends, and white and red in the centre, sometimes reversed, sometimes with yellow instead of red; frequently the blue passes into black, at the extremities of the prism.
These stones are usually found in hexagonal rounded prisms, in layers in the earth, or beds of rivers and streams, in various parts of the globe, never in a transparent crystal in any rock matrix, although the opaque variety of corundum called emery, is found in rocks in many countries. Where rubies and sapphires are met with, gold is almost sure to be present.
The finest rubies occur in the kingdom of Ava. in Siam. in the Capelan Mountains, ten days’ journey from Syrian, a city in Pegu. They are also found in Ceylon, at Hohenstein on the Elbe, in the Rhine and Danube, in Brazil, Hindustan, Borneo, Sumatra, in Australia, in France, in the rivers Espailly in Auvergne and Iser in Bohemia, etc. etc.
The ruby mines of Burmah, whence come the finest stones, have long been known, and the king is said to possess the rarest and most wonderful specimens. They are worked by sinking shafts, until the ruby-producing soil is met with, which occurs at various depths, sometimes within two feet of the surface, sometimes thirty feet below it; when this stratum is found it is followed up until it becomes necessary to sink another shaft, or until it is exhausted; the stones found are almost always small, and seldom free from defects; the rhombohedral crystals are rarely perfect, and usually worn down into rounded surfaces.
These mines are rigorously guarded, no European being allowed to approach them on any pretence. They are a royal monopoly, and fine stones can only be smuggled away, as the order is to retain all for the king’s treasury. When a particularly large and fine stone is found, it is usual to send out a procession of grandees with soldiers and elephants to meet it.
One of the titles of the king of Burmah is Lord of the Rubies. In Ceylon, whence occasionally come some fine rubies, they are found in the beds of rivers; the blue variety, the sapphire, is much more frequently met with, and the crystals are generally found of a much larger size than those found in Burmah.