TOPAZ. 19J> 



Cornwall, etc ., afford smaller crystals. The physalite varie. 

 ty occurs in crystals of immense size at Finbo, Sweden, in 

 a granite quarry, and at Broddbo, in a boulder. A well 

 denned crystal from this locality, in the possession of the 

 College of Mines of Stockholm, weighs eighty pounds. Al- 

 tenberg in Saxony, is the principal locality of pycnite. It is 

 there associated with quartz and mica. 



Trumbull, Conn., is the principal locality of this species in 

 the United States. It seldom affords fine transparent crystals 

 except of a small size : these are usually white , occa 

 sionally with a tinge of green or yellow. The large coarse 

 crystals sometimes attain a diameter of several inches, 

 (rarely six or seven,) but they are deficient in luster, usually 

 of a dull yellow color, though occasionally white, and often 

 are nearly opaque. . , 



The ancient topazion was found on an island in the Red 

 Sea, which was often surrounded with fog, and therefore 

 difficult to find. It was hence named from topazo, to seek. 

 This name, like most of the mineralogical terms of the an- 

 cients, was applied to several distinct species. Pliny de- 

 scribes a statue of Arsinoe, the wife of Ptolen y Philadelphus, 

 four cubits high, which was made of topazion, or topaz, but 

 evidently not the topaz of the present day, nor chrysolite, 

 which has been supposed to be the ancient topaz. It has 

 been conjectured that it was a jasper or agate ; others have 

 imagined it to be prase, or chrysoprase. 



Uses. Topaz is employed in jewelry, and for this purpose 

 its color is often altered by heat. The variety from Brazil 

 assumes a pink or red hue, so nearly resembling the Balas 

 ruby, that it can only be distinguished by the facility with 

 which it becomes electric by friction. The finest crystals for 

 the lapidary are brought from Minas Novas, in Brazil. From 

 their peculiar limpidity, topaz pebbles are sometimes denomi- 

 nated gouttes d'eau. When cut with facets and set in rings, 

 they are readily mistaken, if viewed by daylight, for diamonds. 

 The coarse varieties of topaz may be employed as a substi- 

 tute for emery in grinding and polishing hard substances. 



Topaz is cut on a leaden wheel, and is polished on a cop- 

 per wheel with rotten stone. It is usually cut in the fonr 

 of the brilliant or table, and is set either with gold foil or 

 jour. The white and rose-red are most esteemed. 



What are the uses of topaz '? What is the effect of heat ? 



