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UNIVERSITY OF VIRGINIA PUBLICATIONS 



I. Quartz-albite porphyrj', near Seminole copper mine, Lincoln County, Georgia. 

 Phenocrysts of quartz, albite, and biotite in a fine-grained groundmass of 

 " quartz and plagioclase feldspar with accessory magnetite, apatite, and pyrite. 

 Coarse spherulitic structure shown in groundmass in places. 



II. Schistose and altered quartz-albite porphyry, same locality as I. Same as I 

 except that sericite developed from metamorphism. 



III. Granite porphyry, 1 mile east of Seminole mine. Rock is considerably altered. 



Mineral composition essentially the same as I and II. Some biotite and 

 much epidote present. 



IV. Biotite gneiss. Bell shaft, Columbia gold mine, McDufBe County, Georgia. 



Contains feldspar (plagioclase and orthoclase), quartz, and biotite, with 

 accessory magnetite and secondarj' chlorite, muscovite, and calcite. 



V. Mica schist, Columbia gold mine, McDuffie County, Georgia. Contains quartz 

 and sericite, with some plagioclase feldspar, chlorite, calcite, and pyrite partly 

 altered to iron oxide. 



VI. Mica schist, Parks gold mine, McDufEe County, Georgia. Composition same as 

 V except that mica is less abundant and much epidote is present. 



The norms of the rocks represented by the analyses in columns I, 

 II, III, and IV are as follows : 



Norms of quartz-albite prophyry (J and II), granite porphyry (III), and gneiss {IV), 

 Lincoln and McDuffie Counties, Georgia. 



Quartz 



Orthoclase. . . 



Albite 



Anorthite 



Corundum. . . 

 Hypersthene 



Hematite 



Ilmenite 



Magnetite. . . 



Titanite 



Pyrite 



Apatite 



Calcite 



HoO 



1.67 

 51-35 

 3.61 

 3.47 

 7.9S 



0.76 

 1.62 



32. SS 

 17.79 

 29.34 

 3.89 

 7.14 

 3.29 



1.37 

 1.86 



0.36 



36.36 

 0.56 

 28.82 

 27.52 

 0.10 

 1.02 

 3.20 



34.32 

 10.56 

 20.96 

 10.56 

 6.02 



0.93 

 0.50 

 3.76 



99.44 



101.08 



The position of the rocks in the quantitative classification of igneous 

 rocks may be summarized as follows: 



