ORIGIN. 71 
(O. 
Pattersonite. Pennsylvania. Alteration r>roduct. 
74. Penninite. Georgia and North Carolina. In peridotite. Alteration i»rodn(t. 
75. Picotite (vai'. spinel). In ])eridotite. Primary. 
7);. Picrolite (var. serpentine). Georgia, North Carolina, and Pennsylvania. 
In peridotite and serpentine. Alteration pi-odnct. 
77. Prochlorite. Most common chlorite in (Jeorgia and North Carolina. In 
l)eridotite. Alteration prodnct. 
IS. Pyrite. Gneisses and schists. 
70. Pyrophyllite. Hock constitnent. Regional metaniorphism. Alteration ])rod- 
nct. 
Pyroxene. See varieties. Primary. 
80. Quartz. Rock constitnent. Also in peridotite. Alteration product. 
81. Rhodolite (var. garnet). Cowee Valley, Macon County, N. C. Embedded in 
ruby corundum crystals. 
Ripidolite. See Clinochlore. 
82. Rutile. In amphibole-schists, etc. Contact metaniorphism. 
88. Serpentine. Rock constituent. Also in i)eridotite. Alteration pi-odnct. 
Sepiolite. See Meerschaum. 
Sillimanite. See Pibrolite. 
84. Spinel. Virginia and North Carolina. In peridotite. Primary. 
85. Staurolite. North Carolina. In amphibole-schist. Contact metaniorphism. 
80. Talc. Common in peridotite and pyroxenites. Alteration product. 
87. Tourmaline. Contact metaniorphism. Also (in North Carolina) alteration 
product. 
88. Tremolite. Rock constituent. 
Vermiculite. See varieties. 
89. Villarsite. North Carolina. In peridotite. Alteration product. 
00. Wellsite. Buck Creek mine, North Carolina. In peridotite. Alteration 
product. 
91. Willcoxite (vermiculite). North Carolina. In peridotite. Alteration 
product. 
92. Zircon. Greenwood, Me. In mica-schist. 
93. Zoisite. Georgia and North (\arolina. In jx'ridotite. Alteration product. 
ORIGIN OF COKUIS^DLM. 
During recent years synthetical mineralogy has come to play a very 
important part in the study of mineralogy and geology, and has 
nided considerably in the solving of many geological problems. Thus, 
in working out the problems relating to the origin of corundum in 
the various rocks, the different methods of producing corundum 
artificially have been of material assistance. For this reason these 
methods are briefly described before a discussion of the origin of this 
mineral is taken up. 
ARTIFICIAL PRODUCTION OF CORUNDUM. 
The methods by which corundum has been produced artificially 
are very varied and the results very satisfactory, the corundum being 
obtained in many forms and colors. The artificial production of 
conmdum gems was the motive for the first attempts of this kind, 
