Jackson, Ian. Northumberland Rocks — 50 extraordinary rocky places that tell the story of the Northumberland landscape. Newcastle upon Tyne : Northern Heritage, 2021. The richly illustrated and accessible book series of Northumberland, Cumbria and Durham Rocks are available to purchase from Northern Heritage.
11 Coquet Valley
Theme: Volcanoes and molten rock
Location
Anywhere upstream of Alwinton
Description
If you enjoy treasure-hunting then you might want to explore the shingle banks of the River Coquet between Alwinton and Blindburn and search for agates.
These beautiful small stones, which geologists call amygdales, contain concentric bands of quartz of different colours. Because of their attractiveness they are often used in jewelry.
The agates originated in cavities in the Cheviot volcanic rocks. These cavities were once gas bubbles, vesicles, that were filled with hot mineral-rich fluids which then slowly cooled and crystallised. The agates then weathered out of the rock and were carried downstream by the river. The volcanic lavas that the agates were once part of are about 400 million years old and from the Devonian period of Earth’s history.
While the Coquet valley is a good place to look for agates, you could search almost any valley or stream that drains the Cheviot volcanic rocks.
Dippers, common sandpipers and grey herons are common, and oystercatchers breed on the shingle. The volcanic lavas are locally quite rich in calcium, so that lime-loving plants like hairy rock-cress and quaking grass occur on rocky outcrops by the river. You may see feral goats on the nearby hills.