CORUNDUM (RUBY): DISTINCTION FROM OTHER RED STONES 281 



capacity. However this may be, there is no immediate prospect of the artificial ousting 

 the natural product. 



Other investigators, experimenting in the same direction, have been successful in 

 producing crystals of corundum, notably J. Morozewicz. His fused silicates yielded crystals 

 of spinel as well as of corundum. The corundum crystals were tabular in habit and reached 

 a diameter of 1-5 millimetres. TTie various colours — red, blue, yellow, and greenish-yellow 

 — of these crystals must have been due to the presence of iron, for in the experiments of this 

 investigator chromium was not an ingredient of the fused mass. 



The peculiar, fine carmine-red rubies of considerable size and unknown origin, which 

 appeared in the market in 1885 at Geneva, may be mentioned here. They have the 

 hardness and specific gravity of the natural mineral, but are less brilliant, and in ail 

 probability are artificial products. The colour as seen in the spectroscope is more like that 

 of the artificial crystals prepared by Fremy than of natural crystals, and, moreover, certain 

 appearances under the microscope point in the same direction. The origin of these stones is 

 mysterious, and, if artificial, nothing as to their mode of preparation is known. According to 

 one report they have been formed by fusing together several small rubies ; this, however, is 

 scarcely credible, since at the extremely high temperature of the melting-point of corundum 

 the ruby assumes a dull grey colour. Some authorities again have supposed them to be 

 formed by a method analogous to Fremy's, while yet others have supposed each stone to 

 consist of several small rubies held together in a matrix of glass of the same colour and 

 refractive index. The success which has been attained so far in the artificial production of 

 rubies is encouraging, and affords grounds for the hope that still greater achievements will 

 be possible to future investigators. 



Distinction fuom other red stones. — It is only natural that attempts should be made 

 to substitute for the costly ruby some less valuable stone of similar colour. The two stones 

 most frequently passed off as, and mistaken for, rubies are spinel and garnet. The so-called 

 rubies of cheap jewellery are in reality either the variety of spinel, known as " ruby-spinel," 

 or red tourmaline (rubellite), while topaz may be substituted for pale red ruby. Red 

 quartz will scai'cely pass as a substitute for ruby, but red glass (paste) is frequently so 

 passed off". 



The crystalline form of the above-mentioned substitutes will, if exhibited, serve 

 to distinguish each from the ruby. In either the rough or cut condition, spinel, garnet, and 

 glass may be readily distinguished from ruby by their single refraction and the absence in 

 them of dichroism. Red tourmaline and quai'tz have a much lower specific gravity than 

 ruby ; the latter sinks heavily in methylene iodide, while the two former float easily. 

 Rose-red topaz can only be substituted for pale rose-red ruby ; since there is little difference 

 between them in value it is not so important from a pecuniary point of view to be able to 

 distinguish the one from the other. The specific gravity, however, affords a distinguishing 

 characteristic, since topaz (sp. gr. = 3'5) floats in the heaviest liquid, while ruby (sp. gr. = 

 4-0) sinks. One can scarcely fail to distinguish the ruby, from any stone which may be 

 substituted for it, by its great hardness. After the diamond corundum is the hardest of all 

 known minerals, and will scratch any of the stones mentioned above with ease. 



The word ruby is often used in the designation of stones belonging to mineral species 

 other than corundum. Rose-quartz, for instance, is known as " Bohemian ruby," rose-red 

 topaz as "Brazilian ruby," red garnet as "Cape ruby," and also as "Adelaide ruby"; 

 "Siberian ruby" is the name given to red tourmaline (rubellite), and "false ruby" to red 

 fluor-spar ; while certain varieties of spinel are referred to as " ruby-spinel " and " balas- 

 ruby." 



