462 Sterrett — Tourmaline from San Diego County, Col. 





ment, but the scalenohedron is a steeper one, it (3251), and 

 fig. 6 is here introduced for comparison. 



The features of a third type are the number of prism forms 

 and two bases, generally well developed, with subordinate 

 rhombohedrons 6>, r' and e\ as shown in tig. 7. The crystals 

 are, as a rule large ; 7 ctn high and 3 cm thick not being uncom- 

 mon. The development of the rhombohedrons o and r' some- 

 times varies, with a consequent variation of the base ; this forms 

 a connecting link with the first type ; for some crystals have 

 only a small base with large o faces ; if c were to fail entirely, 

 the crystal might be considered of the first type. 



o\h 



m 



Fig. 6. Brown tourmaline from 

 Gouverneur, N. Y. , with scalenohedral 

 development for comparison with fig. 5. 



These crystals display a most remarkable variation of color, 

 often of a quality unsurpassed by tourmaline from other locali- 

 ties. As an example, a description of one of the numerous 

 crystals in Mr. Schernikow's collection will answer. Begin- 

 ning with the lower end there is a layer of fine green ;* above 

 this, bluish green fading into light rose color ; then sea-green 

 passing into smoky brown or brownish green ; on this comes a 

 cap of dark pink, appearing scarlet by reflected light. All of 

 these colors, with the exception of the smoky brown, are trans- 



