CATALOGUE OF GEMS AND PRECIOUS STONES. 105 



"Spanish/' "smoky," and "false topaz." These stones vary rather 

 widely in hardness and specific gravity, which, together with the 

 power of developing frictional electricity possessed by the true topaz, 

 furnishes a ready means for their discrimination. Thus: 



Name. Hardness. |P«g? 



Oriental topaz 9 4. 01 



True topaz 8 3. 53 



Scotch topaz, etc 7 2. 65 



Topaz occurs in gneiss or granite, associated with tourmaline, mica, 

 beryl, etc., and occasionally with apatite, fluorite, and cassiterite; 

 occurs also in certain talcose rocks, in mica slate, in rhyolite, and in 

 alluvial deposits and drift (fig. 12). It is cut facetted and the better 

 grades are highly valued as a precious stone. 



LIST OF SPECIMENS. 

 BRAZIL (MINAS GERAES). 



Rose, elliptical girdle; pale pink; 14.705 carats; 25 by 17 by 3.5 mm No. 280 



Step-brilliant, rectangular girdle; pale violet-red; 6.54 carats; 13 by 11.5 



by 5 mm No. 281 



Step-brilliant, elliptical girdle; pale yellow; 5.94 carats; 13 by 10 by 5.5 



mm No. 270 



Step-brilliant, elliptical girdle; pale pink; 5.77 carats; 14 by 8 by 6.5 mm. No. 314 

 Step-brilliant, elliptical girdle; pale violet-red; 5.65 carats; 14 by 10 by 



5 mm No . 282 



Rose, pear-shaped girdle; pale pink; 5.57 carats; 14 by 10 by 6 mm No. 283 



Step-brilliant, elliptical girdle; pale pink; 4.569 carats; 15 by 9 by 4 mm.. No. 315 

 Step-brilliant, irregular elliptical girdle; pale violet-red; 4.035 carats; 11 



by 10 by 4 mm No. 284 



Step-brilliant, square girdle; pale yellow; 3.89 carats; 10 by 5.5 mm No. 271 



Step-brilliant, elliptical girdle; pale red-orange; 3.605 carats; 12 by 9 by 



5.5 mm No. 288 



Step-brilliant, square girdle; pale pink; 3.398 carats; 10 by 4.5 mm No. 285 



Step-brilliant, elliptical girdle; pale orange-yellow; 3.24 carats; 11 by 8 



by 5 mm No. 272 



Step-brilliant, rectangular girdle; pale violet-red; 3.06 carats; 10 by 8 by 



5 mm No. 287 



Step-brilliant, elliptical girdle; pale red-violet; 2.96 carats; 12 by 8 by 4 



mm No. 292 



Step-brilliant, pear-shaped girdle; pale red-violet; 2.918 carats; 16 by 6.5 



by 4 mm No. 286 



Step-brilliant, rectangular girdle; pale pink; 2.89 carats; 10 by 8 by 4 mm. No. 316 

 Step-brilliant, elliptical girdle; pale pink; 2.85 carats; 12 by 7.5 by 4 mm. No. 289 

 Step-brilliant, rectangular girdle; very pale violet-red; 10 by 8 by 5 mm... No. 297 

 Step-brilliant, rectangular girdle; pale violet-red; 2.79 carats; 9 by 8 by 



5 mm Xo. 294 



Double-rose, elliptical girdle; pale violet-red; 2.7 carats; 7 by 6 by 6 mm.. No. 303 

 Step-brilliant, pear-shaped girdle; very pale red-violet; 2.59 carats; 15 by 



6 by 4 mm No . 293 



4555—22 -9 



