266 PRECIOUS STONES. 



number of minerals, crystals of two inches are almost gigantic; few, in- 

 deed, exceed four inches in height. Quartz, however, forms an exception 

 to this rule. Specimens are brought from Madagascar more than twelve 

 inches in length and remarkably pure and transparent, notwithstanding 

 their great size. The rock crj^stal of this island is used for the object 

 glasses of astronomical telescopes. Magnificent crystals have also been 

 found in the Alps ; one of these Alpine crystals, taken in Italy by the 

 French, was borne in triumph to Paris in 1797. There is a beautiful speci- 

 men in the Museum of Natural History at Paris, which measures three 

 feet every way, and weighs nearly 800 pounds. At the French Exhibition 

 of 1866, in the sections of Japan and Brazil, there were some wonderful 

 crystals. One brought from Brazil weighs 212 pounds, is 2^ feet high, 1 

 foot in diameter, and is a perfect six-sided prism. A remarkable j)henome- 

 non m quartz is exhibited by the fluid drops contained in many specimens. 

 Sir David Brewster ascertained that the fluid is not water, but of an ole- 

 agineous nature, one part volatile at 27 degrees, and the other a fixed oil. 

 Dana has named the former cryptoline and the latter brewsterine. Some 

 beautiful specimens of quartz crystals, beaded with those imprisoned drops, 

 have been foiTud at Trenton Falls. 



" Quartz has but little value of its own ; but when it is made into vases, 

 cups and other artistic objects, it acquires a high price. The Athenians 

 produced some exquisite works of art in rock crystal, and the Eomans 

 valued it very highly in the form of vases. ISTero had two cups of it, which 

 he broke in his rage, when he heard of the revolt that caused his downfall. 

 One of these cups was estimated at over $1,900. The elegants of Eome 

 were in the habit of using balls of rock crystal to cool their hands, and 

 certain occult charms were also said to reside in these smooth, cold globes. 

 In the middle ages the Yenetians j^roduced some beautiful objects in rock 

 crystal ; and Milan has long been famous for its statuettes, vases and giran- 

 doles of this material. But desire of gain has deteriorated the artistic value 

 of these productions. Cut crj^stals have come to be sold by weight, and 

 the cutting is naturally falling into neglect. In the Cathedral at Milan the 

 burial shrine of St. Charles Borromeo is wholly formed of plates of rock 

 crystal of six or eight inches square each, set in a framework of silver. 

 The shrine was the gift of Philip lY of Spain, who employed eight years 

 in collecting the necessary quantity of rock crystal." 



"When crystals of quartz are found combined with certain traces of col- 

 oring matter, they constitute distinct species in commerce, and take com- 

 pletely different names. Combined with iron and alumina, quartz becomes 

 yellow and takes the name of the Bohemian topaz. Impregnated with a 

 bituminous substance it becomes more or less darkened, and is called the 

 smoky topaz. Combined with a slight proportion of oxide of manganese it 

 takes a beautiful violet color; it is then the occidental amethyst. Colored 

 blue by iron and alumina it becomes the water sapphire. Colored rose by 

 iron and manganese, it is the Brazilian ruby. Combined with a notable pro- 



