Silverstone is a famous motor-racing track in south-central England. The British Grand Prix — Britain’s big international car race — is held there. The circuit was built on an old wartime airfield; after the war, people started racing on the runways, and the place became one of the great names in Formula One. When English speakers say Silverstone in a sports conversation, they almost always mean the track and the race weekend, not the small village next door, though the village is where the name comes from. It is a place name, so it takes a capital S. You do not say “a silverstone,” and you do not treat it as a kind of stone.