The magnetic ‘mountain’ - The geology of the North West Highlands 2024 Trip. My guest Brian showing us how this rock is magnetic with a magnet 🧲. The Banded Iron Formation (BIF) near Gairloch, Scotland, is an ancient geological feature dating back to the Paleoproterozoic era, around 2.4 billion years ago. BIFs are distinctive sedimentary rocks consisting of alternating layers of iron-rich minerals and silica (typically in the form of chert), and they hold key clues to Earth’s early atmospheric