The old volcanic rocks of the Scottish coast and glens weather out agates the Victorians called “Scotch pebbles,” banded in red, blue and grey, and prized enough to floor a whole jewelry trade. The Usan and Ferryden shore near Montrose, the Ayrshire coast and the Ochil and Sidlaw hills are the classic grounds. Foreshore collecting is often allowed below the high-tide line; the famous inland sites are mostly on PRIVATE farmland, so ask.
Agate (Scotch pebbles)
See it on the map
Other places on the map within a couple of hours.