Cobbles - 4

Many of the cobbles along the shore come from very ancient rocks to the east of Kilchoan, They may originally have been sedimentary rocks such as sandstones, muds and clays but, during an intense mountain-building event, were deeply buried, cooked, and subjected to huge pressures. They didn't quite melt, but their minerals were completely changed.

The one above may have been a slightly muddy sandstone but it's now a gneiss; and gneisses are about as cooked as these metamorphic rocks get before they melt and produce magma which later cools to form igneous rocks such as granite.

The prettiest metamorphic rocks are the schists, which haven't been cooked quite as much as the gneisses and, because they have more clay minerals in their orginal rocks, contain a lot of mica. The mica is flaky and shiny. This particular one has developed another characteristic metamorphic mineral - garnet.

The garnets, which are red, are clearly seen in this close-up. It's probably almandine garnet. the most common variety.

The nearest metamorphic rocks to Kilchoan are to the east, just the other side of Loch Mudle. They are called the Moine Schists, the word moine being Gaelic for peat or moor. There's a good, freshly exposed outcrop of these garnet-mica schists in the road cutting at Salen, on the opposite side to the Salen Hotel.