GEOLOGY OF GRAVES MOUNTAIN 215 



describe and -work it. According to Kunz* the rutile from this locality has 

 realized at least ■'§20,000 for cabinet specimens and has supplied the col- 

 lections of the world. The rutile was won from the central depression on 

 top of the ridge and along the northwest slope. The openings are of long 

 standing and had so greatly caved at the time of the senior author's visit 

 in March, 1911, that they were largely obscured. 



No specimens of coarse rutile were observed by the senior author during 

 his visit but it is plentiful in every specimen collected, chiefly as microscopic 

 inclusions in other minerals and frequently as small crystals and grains visi- 

 ble to the naked eye. It has been observed megascopically in the quartzite, 

 and in intimate association •ndth cyanite, lazulite, pyrophyllite, and hema- 

 tite. As a microscopic accessorj' rutile in crystals and formless grains of 

 red and reddish-brown color has been identified as inclusions in the lazulite, 

 cyanite, pyrophyllite, hematite, and quartz, and formed along the bound- 

 aries of these minerals. In each case it shows the usual optical properties. 



Veatchj observed rutile with quartz and iron oxide in veins not exceed- 

 ing a few inches in ^\adth on top of the mountain. The rock fragments 

 thro'W'n out of the small pits on top of the mountain show fracturing and 

 brecciation, and formation of the vein rutile was probably subsequent to 

 the fracturing of the quartzite but a part of it may have existed in the veins 

 prior to the crushing. 



The coarse rutile crystals from this locality observed in the various 

 mineral collections in this country are lustrous black to reddish-brown and 

 red, with brilliant orange red in thin crystals. They vary in size usually 

 up to 5 inches and occur both as single and twin forms. Kunzf reports 

 fine single crystals have been found up to four pounds each and with it very 

 interesting hydrous anthophyllite. 



The single crystals are usually prismatic with frequently pyramidal 

 terminations shown. 



Besides the common forms of rutile crystals this locality has furnished 

 some rather rare and interesting ones, which have been figured and de- 

 scribed chiefly by German crystallographers, § especially Rose, Haidinger, 

 vom Rath, and Miigge. Especially interesting are the beautiful rutile 

 twins figured and described by Rose and others, composed of as many as 

 six- and eight-fold twins commonly kno^vn as sixlings, and eightlings; 



* Kunz, G. F., N. C. Geol. Survey, Bull. 12, 1907, p. 52. 

 t Personal communication, January, 1912. 

 + Personal communication, February 28, 1910. 



§ See Dana, E. S., A System of Mineralogy; and Hintze, C, Handbuch der Miner- 

 alogie for references. 



