The Virtual Rock Kit -

Rock 8: Pyrophyllite phyllite

This rock is composed almost entirely of the mineral pyrophyllite.   Pyrophyllite is a soft mineral (with a hardness of 1 on the Mohs hardness scale) formed by the hydrothermal alteration of volcanic deposits.  The volcanic deposits were altered as hot fluids permeated ancient ash deposits.  Pyrophyllite is mined in Hillsborough for use in high temperature ceramics (e.g. spark plugs).  The term phyllite is used to indicate that the rock is a very fine-grained, foliated metamorphic rock - similar to slate but distinguished by its sheen, which is produced by barely visible flakes of mica or other platy mineral. 

Pyrophyllite phyllite

pyrophyllite phyllite sample

Please remember that rock and mineral collecting is STRICTLY PROHIBITTED on protected land!



Want to learn more about the geology of the Eno River area?

You may be interested in A Geologic Adventure Along the Eno River - A richly illustrated publication from the North Carolina Geological Survey.