CATALOGUE OF GEMS AND PRECIOUS STONES. 137 



place on a gigantic scale, even to the formation of individuals several 

 feet in length, though as a rule much smaller. At times the quartz 

 and feldspar crystallize contemporaneously in long, parallel, skeleton, 

 and enfolding prisms, giving rise to forms which when cut across 

 resemble ancient Greek or Phoenician characters. Such forms are 

 called graphic granite. The quartz and feldspar of the pegmatites 

 are mined for use in pottery manufacture, the mica for electric and 

 other purposes, while the beryls and the tourmalines, if of good color, 

 are utilized as gems. 



The pegmatites are common features of granitic rocks, and are 

 found in greater or less abundance in nearly all of the states along 

 the Appalachian chain, as well as in many of the regions west of the 

 front range of the Rocky Mountains. 



Two collections of these interesting rocks are shown, one from the 

 Appalachians of the eastern United States, and one from the cele- 

 brated gem regions of southern California. Each comprises upward 

 of 100 specimens showing the rocks in the rough and cut and 

 polished conditions, and the associated minerals. In each case, and 

 in the California series in particular, space is given to the decomposed 

 and disintegrated material from the middle or "pay streak" portion 

 together with examples of the same amount of material separated 

 into its component minerals. The gem minerals from the California 

 region, it should be mentioned, are mainly tourmalines of a pink 

 and green color, and the variety of spodumene known as kunzite. 

 Those from the Appalachians are mainly green tourmaline and the 

 variety of beryl known as aquamarine. 



A. THE APPALACHIAN PEGMATITES. 



Among the more prominent objects in the Appalachian series are 

 several large specimens showing (1) a pegmatite intrusion some 6 

 inches in width in gneiss, from Auburn, Maine (39058), (2) one of 

 similar nature, 4 inches in width, bordered by a thin black tourmaline, 

 in granite, from Cape Elizabeth, Maine (62508), (3) a thin zone of 

 pegmatitic material with very obscure outlines in the Rockport, 

 Massachusetts, granite (38757). There is also a large rough pegma- 

 tite from Amelia, Virginia (88983), and a fine large polished slab 

 from Auburn, Maine (74795), cut across the grain, showing to advan- 

 tage the " graphic" structure. Among the smaller and associated 

 minerals are crystals of muscovite, showing the characteristic hexago- 

 nal outline (62377), masses of the lithia mica, lepidolite (90229), and 

 the feldspar orthoclase or microcline (49700), amazonstone (48721), 

 and albite (48723); also large masses of black tourmaline (89944); 

 green radiating tourmaline in matrix (82268, 89939) and examples 

 of beryl (90244), including the variety emerald in matrix from North 

 Carolina (53778). The gem minerals (90223) occur associated mainly 



