CATALOGUE OF GEMS AND PRECIOUS STONES. 107 



Ural Mountains. 



Step, rectangular girdle; colorless; 12.816 carats; 19 by 11 by 7 mm No. 263 



Brilliant, elliptical girdle; colorless; 4.165 carats; 12 by 9 by 6 mm No. 264 



Step-brilliant, elliptical girdle; pale blue; 2.05 carats; 10 by 8 by 3 mm No. 265 



SCOTLAND. 



Step, square girdle; pale blue; 3.525 carats; 10 by 5 mm. Isaac Lea collec- 

 tion No. 269 



UNITED STATES. 



Colorado. 



Brilliant, rectangular girdle; culorless; 17.77 carats; 17 by 12 by 10 mm No. 319 



Step-brilliant, rectangular girdle; red-brown; 14.626 carats; 19 by 14 by 6 mm. 

 Isaac Lea collection No. 318 



Maine. 



Stoneham, Oxford County: 



Brilliant, square girdle; colorless; 2.875 carats; 9 by 6 mm No. 324 



New Hampshire. 



Baldface Mountain, Chatham, Carroll County: 



Brilliant, circular girdle: colorless; 12.357 carats; 15 by 9 mm No. 323 



Utah. 



30 miles southwest of Salt Lake City, Salt Lake County: 



Brilliant, circular girdle; colorless; 1.46 carats; 7 by 5 mm No. 320 



Brilliant, circular girdle; colorless; 1.369 carats; 7 by 5 mm No. 321 



Brilliant, circular girdle; colorless; 0.89 carat; 5.5 by 4 mm. Isaac 



Lea collection No. 322 



TOURMALINE. 



Varieties. — Achroite, colorless; indicolite, blue; rubellite, pink. 



Composition. — A complicated boro-silicate of magnesium, iron, 

 aluminum, and alkali metals. 



Crystallization. — Hexagonal (trigonal), hemimorphic; habit usually 

 prismatic with strong vertical striation and different terminal faces 

 at the opposite ends of the crystal. 



Color. — Colorless when containing but traces of iron, but usually 

 colored intensely blue, green, brown, pink, to dense black, etc., by 

 iron, manganese, chromium, or possibly other elements; strongly 

 pleochroic. 



Luster. — Vitreous; transparent to translucent and opaque. 



Hardness. — 7 ; a durable stone. 



Specific gravity. — Varying considerably with composition, but 

 averaging 3.1. 



Optical properties. — Mean refractive index varying with the com- 

 position, but usually about 1.65; double refraction moderately strong, 

 0.02; optically uniaxial, negative. 



