This large, blackish Grimmia was only confirmed as a British and Irish species in 2007 and it remains unfamiliar to many bryologists.
Although its large, dense cushions are conspicuous when growing on hard, south-facing rocks, it is essentially a microscope-only species. It’s especially fond of basic volcanic rocks, including dolerite, basalt and peridotite.
Clusters of spherical red-brown leaf gemmae have been reported from European specimens but are rare here.
To identify this species, you’ll need a modern key, and fortunately there are several available from the Resources pages of this website.