41. Beecraigs Quarry in Beecraigs Country Park
Beecraigs Quarry shows a good section through an east-west trending dyke about 30m across, a type of igneous intrusion formed when magma rose along a nearly vertical crack through existing rocks about 300 million years ago.
The dyke is quartz-dolerite, a variety of dolerite that contains small amounts of quartz. This igneous rock displays horizontal columnar jointing, as opposed to the more usual vertical jointing often found in lava flows. The margin of the dyke, which can be seen at the top near the railings, has smaller crystals because it cooled more quickly.
The quarry is currently used as an outdoor climbing wall. The exposures are maintained, so they are easily accessible and safe. A dry stone dyke lining the road is made of quartz-dolerite. The quarry is in the south-east corner of Beecraigs Country Park, with easy access from the car park. Nearby geodiversity sites are Hilderston Silver Mine Quarry (28) and Cockleroy Hill (40).
