Many observers, both in this country and abroad, have noted the alteration exteriorly of allanite to usually a reddish brown product whose general appearance on casual examination seemed to be closely similar. This alteration is frequently conspicuous in localities where allanite is found at or near thé surface in lumps and masses, and is shown especially well at places in some of the Atlantic States, particularly in Virginia, in the Carolinas, in Pennsylvania, and in Texas, and in specimens examined by the writer from other localities in the United States and abroad.
Some of the more important localities have been studied in the field and collections made of the fresh allanite and its alteration product for laboratory study. During the progress of the investigation certain fundamental questions arose which the writer had assumed as settled, but which are now regarded by him to be at least doubtful. Chief among these . . .