Untitled Document

The Hillsborough Caldera

At Occoneechee Mountain, hydrothermal fluids removed silica and other elements from the ash deposit. The altered ash was later metamorphosed into pyrophyllite.

Pyrophyllite (AlSi2O5OH) has a structure similar to talc, with a hardness of 1. It can be scratched with fingernails. It is used in ceramics, heat-resistant products (refractories), and in paints.