288 DESCRIPTIONS OF MINERALS. 



Saxony, is the principal locality of pycnite. It is there as- 

 sociated with quartz and mica. 



Trumbull, Conn., is a prominent locality of this species 

 in the United States, It seldom affords fine transparent 

 crystals, except of a small size ; these are usually white, oc- 

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

 crystals sometimes attain a diameter of several inches (rare- 

 ly six or seven), but they are deficient in lustre, usually of 

 a dull yellow color, though occasionally white, and often 

 are nearly opaque. It is found also at Crowders Mountain 

 in X. C. ; in Utah, in Thomas's Mountains, and in gold 

 washings in Oregon. 



The ancient tojmzion 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 mineral ogical terms of the an- 

 cients, was applied to several distinct species. Pliny describes 

 a statue of Arsinoe, the wife of Ptolemy Philadelphus, four 

 cubits high, which was made of topazion, or topaz, but evi- 

 dently 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 

 supposed it to be prase or chrysoj)rase. 



Topaz is employed in jewelry, and for this purpose its 

 color is often altered by heat. The variety from Brazil as- 

 sumes 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. Beautiful crystals 

 for the lapidary are brought from Minas Xovas, in Brazil. 

 When cut with facets and set in rings, they are readily mis- 

 taken, if viewed by daylight, for diamonds. From their 

 peculiar limpidity, topaz pebbles are sometimes denomi- 

 nated gouttes cTeau. 



The perfect cleavage of topaz makes it a poor substitute 

 for emery. 



Euclase. 



Monoclinic. In oblique rhombic prisms, with cleavage 

 highly perfect parallel to the clinodiagonal section, afford- 

 ing smooth polished faces. 



Color pale green to white or colorless, pale blue. Lustre 

 vitreous; transparent. Brittle. H.=7*5. G.=3\L. Pyro- 

 electric. 



