In order of solubility the rocks of the Catoctin Belt, within the limits of Loudoun County, to which section all subsequent geologic data will be confined, stand as follows:
1. Newark limestone conglomerate; calcareous.
2. Newark sandstone and shale; calcareous and feldspathic.
3. Newark diabase; feldspathic.
4. Granite; feldspathic.
5. Loudoun formation; feldspathic.
6. Granite and schist; feldspathic.
7. Catoctin schist; epidotic and feldspathic.
8. Weverton sandstone; siliceous.
All of these formations are in places reduced to baselevel. The first three invariably are, unless protected by a harder rock; the next three usually are; the Catoctin schist only in small parts of its area; the Weverton only along a small part of Catoctin Mountain.