276 



MINERALOGY 



pink, as in cobalt bloom. Uranium minerals are yellow or green. 

 Molybdenum yields greens and yellows, and tungsten yellow or 

 blue; while the browns and yellows of most quartz, as smoky 

 quartz, are caused possibly by organic matter, and the delicate 

 blues, violets, greens, and yellows of fluorite, apatite, barite, and 

 topazes are also attributed to organic matter. 



Inclusions of colored minerals within the body of a colorless min- 

 eral are often the cause of color in minerals, as the red or flesh- 



FIG. 392. Section of Tourmaline, with an Uneven Distribution of Color. Brazil. 



colored orthoclases of some granites is caused by included scales of 

 hematite, as is also the peculiar appearance of aventurine quartz. 

 The color of minerals caused by pigments is not always evenly 

 distributed, as during the period of growth of some crystals the 

 chemical composition of the mother solution may have changed as 

 regards these minor constituents, resulting in the change of color 

 of the forming crystals, producing phantoms or outlined crystals 

 within the body of larger individuals, as the phantom amethysts of 

 Schemnitz, Hungary, and the phantom fluorides of Cumberland, 

 England. The best illustration of the uneven or irregular distribu- 

 tion of color is the variegated tourmaline of many localities, as of 

 Haddam, Connecticut ; Pala, California, or Brazil. In the latter 

 the colors appear in concentric bands as illustrated in the section, 



