EARTHS. SILICEOUS. 42, Gemma. 143 



Found in Bra/il, the //;i/>r, Perfia, Bohemia, and near Piiys in 

 Fela^, iometimcs cryilalllzed, foinetimes in rounded mafTes, 

 the angles being worn off by friftion, and is next in value to 

 the Ruby: colour Iky-blue, or the fhades of PruifMn and 

 indigo-blue, with fometimes white fpecks: the cryilals arc 

 ilrong, (hining, and exhibit a foliated texture tranfverfely 

 ilriite; they become colourlefs when headed with micros 

 cofmic fait, and emit a great light while burning: fpccific 

 crravity from 3,780. to 4,000. contains alumina 58. filica 

 35. carbonate of lime 0,5. iron 0.2. BergmaH, 



jepazlus. Nearly very hard, ponderous, yellow, of a foliated tex- 

 ture which is conchoidal when broken tranfverfcly, 

 not fufible per fe, but lofing all its colour in a llrong 

 heat- 

 Borax Topa^ius. 5'y/?. r,dt» xii. 3. /. 94 «• 2. a. 

 Gemma pellucidifiima. l^^alL lyst, ip- 239. «. 4* 

 Oriental Topaz. Kirnvan mineral. 1,^.251. 

 Topaz. Schmeijfer mineral. 1, p, 62, 

 Imperfeil Corundum. Thomfon chetn. 3. p, 505. 

 Found in fndi-aj Braftl, RuJJiay Saxony , Bohemia, &:c. gene- 

 i'ally adhering to other fubitances, _though fometimes de- 

 tached with the angles worn off: colour a lighter or deeper 

 yellow, moll commonly honey-colour, fometimes verging to 

 white or greenifh ; its fragments are fometimes irregular, 

 fometimes granular orprifmatic: ths prifms longitudinally 

 ftriate, folitary, in pair?, or in threes dilpofed in a cruciate 

 manner, often clullered, rarely 4-iided, rcftangular or ob- 

 liquangular, more frequently unequally 8-fided terminated 

 hy an irregular 4 or 8-lided pyramid, or ending in a point: 

 is infufible perfe, and lofes its colour only in a very high de- 

 gree of heat : melts with borax and microcofmic fait into a 

 clear glafs : fpecific gravity from 3,531. to 3,564. contains 

 filica 52. alumina 44. carbonate of lime 2. oxyde of iron 

 o, 3 1 . Bergmafic 



Hyacinihus* Hard, lamellar, of a peculiar yellowifli-red, in 4-nde{! 

 prifms terminated both fides by a 4-fided pyramid, 

 not fufible per fe, but lofing its colour in a firong 

 heat. 



Nitrum iapidofum. Syst tiat» xii. 3./. 85. «. 3. a. 



Topazius flave-rubens, Wall.Jyit, i. />. 240. ». 4. i. 



Hyacinth. Kirn/j an mineral. \,p. 257. 



Zircon, Jargon, Hyacinth, Thom/on chm, ^, p, ^2t» 



Hyacinth. Sch^g'J/er mineral, i. p> 6/^. 



found in the Ea/i and Bohemia, in the form of pebbles, in ob- 

 tufe angular pieces: colour yello.vifii-red with a mixture of 

 brown : the cryilals are fmall, have a fmooth furfice ani 



