RUBY, the rich red, transparent variety of corundum, having a hardness" of nine and a specific gravity of four. The name is some tunes used for other red gems (see RUBY SPINEL), and improperly for richly colored gar nets, of the variety pyrope. The stones called Cape rubies and Arizona rubies are only fine py ropes, coming. respectively from the South Afri can diamond mines and from Arizona and New Mexico. (See Pinions). Siberian ruby is a term sometimes applied to gems of rubellite or red tourmaline (q.v.), and Brazilian ruby to the deeper shades of pink topaz, altered to that color by heat. The true rubies recently mined in the Cowee Valley, in North Carolina, have attracted much interest, being in some cases as fine as those from but they are mostly small, and it is not certain whether they will prove of real importance. They occur in a greatly decomposed igneous rock, in the same manner as the very similar crystals of 'sapphire from Yoga Gulch, Montana. The rubies of Burma, formerly spoken of as Pegu, are derived. from a-crystalline limestone.' In these cases, and indeed generally, the gems are largely found in gravels and surface deposits formed from the decomposition of the parent rocks. True rubies of large size are very scarce, so that one of three carats weight, flaw less and of good color, is worth much more than a diamond of the same size. Like all the deeply-colored corundum gems, rubies are strongly dichroic, their color varying with the direction in which light traverses the crystal, whether transverse or parallel to the axis of the prism. The presence of microscopic cav
ities or of included crystals of t int minute ness, disposed in a certain parallelism to the crystalline axes, produces the optical effect known as asterism, which is exhibited by the highly prized gems called star rubies (and star sapphires). In less amount or when irregu larly distributed, the same causes produce de fects known as "silk,') and cloudiness. Many efforts have been made to produce the ruby by chemical means, and a dozen or more processes have been devised with greater or less success within the past 50 years, but with little practical result. Crystals have been obtained, of fine color, but mostly small, or in flat hexag onal plates too thin to furnish gems. Some years ago larger pieces appeared in the market that caused some concern from their close re semblance to natural rubies. The process was not made known, but was judged to be that discovered by Fremy and Feil, by fusing an aluminate of lead with silica. They were de tectable by the microscope, which showed that they contained minute cavities that were rounded and bubble-like, while those in real rubies are angular and crystalline. The French of Diamonds and Precious Stones' decided that all such rubies must be sold as under penalty of fraud.