View of the quarry, west side of Mill Glen, Tillicoultry, Clackmannanshire


Quarry, west side of Mill Glen, Tillicoultry, Clackmannanshire, which shows regional context in which hornsfels is formed - the examples on Arran are on a much smaller scale

Quartz-dolerite of the Ochil Fault-intrusion forms the face to the left of the photographs. Lavas, hornfelsed by an adjacent diorite intrusion, occur at the right (north). Contact of dolerite and hornfels passes up the right side of the prominent rib of rock to skyline.

Quartz-dolerite forms a reliable source of good road metal (aggregate). A variety of current and former crushing plant is seen on the left, while behind and to the left are stockpiles of aggregate.

The Ochil Fault-intrusion comprises five irregular, discontinuous, pod-like bodies of quartz-dolerite intruded along the plane of the Ochil Fault. Hornfelsed rocks are rocks that have undergone recrystallization due to the heat from a nearby igneous intrusion, they are said to have undergone contact metamorphism.

SCRAN ID: 000-000-032-452-C; British Geological Survey