Whinstone in a sentence as a noun

The walls are solid whinstone about 600mm thick which I'd have expected to be a good insulator but in reality they're a thermal bridge. For generation, I've reserved a spot in Rippleenergy's next co-op turbine [0].

Whinstone definitions

noun

any of various hard colored rocks (especially rocks consisting of chert or basalt)

See also: whin