Pratt — Corundtim in North Carolina. 297 



often broken, exhibits rolling extinctions and the albite lamellae 

 are curved and bent. It runs along the planes of schistosity 

 between the feldspars and forms a mosaic of angular broken 

 grains." 



" Staurolite was found in rather broad irregular grains, and 

 the rutile in small irregular grains and well crystallized prisms." 



Prof. Pirsson has indicated that the character and structure 

 of this rock, composed chiefly of amphibole, labradorite and 

 garnet, suggests most strongly that it is a metamorphosed 

 igneous rock of the gabbroid family. During metamorphism, 

 the augite of the gabbro would be converted into the brown 

 hornblende and any iron ore that was present would be taken 

 up by the hornblende and garnet. The rutile would have 

 resulted from the titanic acid that is a regular component of 

 the iron ores in these gabbro or diabase rocks. Staurolite is 

 rather naturally expected, as it is usually a mineral of meta- 

 morphism, and its natural home is in the schistose rocks. The 

 feldspar has suffered the least (except the corundum) chemically 

 and shows only the shearing of dynamic processes. 



The corundum does not occur in crystals but in small frag- 

 ments and in elongated nodules, which are cracked and seamed, 

 and appear to have been drawn out by the shearing processes. 

 The general character and shape of the corundums would indi- 

 cate that they were original constituents of the igneous rock 

 and were not formed during its metamorphism. 



The exact classification of this rock is not easy, but it will 

 probably be nearer correct to bring it under the head of an 

 amphibole-schist. 



Corundum in Quartz- Schist. 



In the crystalline rocks of the southwestern part of North 

 Carolina and the northeastern part of Georgia an interesting 

 occurrence has recently been observed, namely that portions 

 or bands of these are corundum-bearing. These corundum- 

 bearing bands are first encountered on the head waters of 

 Tallulah river, in the northern part of Rabun County, Georgia, 

 and can be followed in a northeasterly direction to the Yellow 

 Mountain in Clay County, North Carolina. They are near the 

 top of the Blue Ridge, at an elevation of from 3000 to 4000 feet. 



The composition of these rocks vary from those that are a 

 normal gneiss to those that contain no feldspar and can best be 

 described as quartz-schist, composed of biotite mica and quartz. 

 Some portions of the rock are rich in garnet, while others are 

 almost entirely free from this mineral, and occasionally there 

 are small bands of white quartz. They are distinctly laminated 

 and are frequently intersected by granitic dikes, some of which 

 are coarsely crystallized and of a pegmatitic character, that are 

 often parallel with the beddings of the schists, although many 



