222 Precious Stones. 



matter influence the mode in which the molecules of alumina 

 are aggregated and the gem produced. Sapphires come next 

 in hardness to diamonds, and rubies of large size, and of the 

 " pigeon's blood" colour, are so rare as to command prices 

 higher than those of diamonds. The oriental emerald, or 

 green sapphire, is, as Mr. Emanuel informs us, " the rarest of 

 all gems, and is scarcely ever seen." Even so large a dealer 

 in these commodities as Mr. Emanuel "has only met with one 

 specimen in the whole course of his experience." 



The foolish whims of fashion in respect to gems seem to be 

 displayed against the yellow sapphire, or oriental topaz. It is 

 a jewel of remarkable beauty, and yet stated to be of very 

 little value in commerce. Those who like gems for their beauty 

 more than for their rarity, should take advantage of these 

 freaks of fashion, and buy those things that have substantial 

 merit when their commercial price is low. Yellow quartz is 

 often called topaz, but it is a very inferior thing to the oriental 

 gem. There are also Brazilian and Saxon topazes, which are 

 fluorides of silica and alumina. 



Thus far we have seen the two most valuable gems, dia- 

 monds and rubies, to be composed of very common materials 

 in an uncommon condition. The opal may be added to this 

 list, being a compound of silica, or flint, with a little water, 

 and minate portions of iron, alumina, etc. The emerald — not the 

 oriental one, or green sapphire — mingles with the common 

 materials, silica and alumina, about 13 per cent, of glucina, 

 a rare earth. Glucinum, of which glucina is an oxide, is a white 

 malleable metal, which few chemists have seen. It fuses below 

 the melting point of silica, and does not burn in air or oxygen. 

 The name glucinum was given from the Greek, ry\vtcvs, sweet, 

 in allusion to the taste of its salts. 



Beryls and emeralds only differ slightly in composition. The 

 finest emeralds come from New Granada, where they occur in 

 a limestone rock. The colour of the emerald was supposed to 

 depend upon its containing a small quantity of oxide of 

 chromium, but Mr. Emanuel inclines to the opinion of Mr. 

 Lewy, who ascribes it to the presence of a vegetable matter 

 analogous to the chlorophyll of plants. 



The zircon, hyacinth, or jacynth affords, like the emerald, 

 a specimen of a gem containing a rare substance mixed with 

 others that are common — the composition showing nearly 67 

 per cent, of zirconia, and the rest silica with a trace of iron. 

 Zirconia is the oxyde of zircon, a metal about which nothing 

 interesting is known. The jacynth is formed of various 

 colours, from red to grey and white. The ordinary specimens 

 look like a tawny emerald, and have little beauty, but fine 

 ones may merit the favour which poets have sometimes bestowed 



