Intergrowths of Allanite "ml Epidote. — Hobbs. 219 
occurrences have been found by other observers which have 
not been reported, and it is likely that others have been 
passed by because they have not been recognized. The nu- 
merous observations which have already been reported are suf- 
ficient to show that allanite-epidote intergrowths have con- 
siderable importance in granitic and gneissic rocks. 
Very recently has appeared a paper by Keves* which gives 
the results of further study of these two minerals in the 
Maryland granites. The special interest of the paper con- 
sists, as is indicated by its title, in the argument for the origi- 
nal nature of the epidote. Epidote has generally been con- 
sidered as always of secondary origin. Kosenbusch expresses 
this view in his '• Physiographic " as follows: " Der Pistazit 
oder Epidote tritt wohl nirgends in den Eruptivgesteinen als 
primarer Gemengtheil aufV'j It has occasionally, however, 
been hinted that such might not always be its nature. In 
discussing the origin of the Ilchester epidote, the present 
writer* called attention to the fact that, though the granite 
of Ilchester is much stretched, similar intergrowths of allan- 
ite and epidote have been found by Prof. Williams in tin- 
Woodstock granite, which shows no evidence of cataclastic 
structure. Dr. Keyes in the paper cited gives the following 
arguments for the original nature of the epidote: Its presence 
in fresh or but slightly altered rocks, the inclusion of the 
mineral in sphene, and the formation of biotite in cracks of 
the epidote. His argument from idiomorphic character 
would not seem to me to be valid, since minerals like Stauro- 
lite and garnet, which can be shown to be of secondary devel- 
opment, frequently possess remarkably well defined idiomor- 
phic outlines. He has, however, as it seems to me, brought 
forward sufficient evidence to show that, in sonic cases at 
least, the epidote of the allanite-epidote intergrowths jv 
original. 
University of Wisconsin, September '.nit, 1898. 
*Epidote as a primary Component of eruptive Rocks. Bull. Geol. 
Soc. Am., vol. iv, pp. 305-312, 1893. 
+Mikroskopische Physiographie (3te Auflage) Stuttgart, 1892, vol. i, 
p. (510. 
^Tschermak's min. und petrog. MittheiluDgen, vol. xi, p. G, 1889. 
