The Rockery - Metamorphic & Igneous Rocks
Richards Mountain Pages
This page contains rocks that have been formed either by heat and pressure, or by molten rock which never broke through the surface of the Earth. Either way, they have cooled slowly in the boughs of the Earth to give these nice crystalline rocks.

Greisen Locations : Hensbarrow Downs - Cornwall Greisen is an unusal form of granite where the feldspars have been replaced. The rock is almost a pure white, though this sample has an attractive pale green colouring. This piece came from around the China Clay mines of St Austell.

Quartzite Locations : Throughout Scotland This specimen came from Binnein Beag, in the upper reaches of Glen Nevis. Its one of the last mountains before the flat expanse of Rannoch Moor. Often mistaken for snow, quartzite is normally white, though it can be discoloured from impurites (as above). Since its basically broken glass, it makes a tooth jarring squeak as you walk across its scree, which also has the tendency to shred boots. As seen on TV :- watch 'Rob Roy' for a view of Sgurr A Mhaim's quartzite cap

Eclogite
Locations : far NW Scotland
This unusual rock is composed of red garnet and green pyroxine, with other minerals present in lumps. It is found in the gneisses of North West Scotland in small quantities, and in particular around Glenelg. This specimen came from the lower slopes of Beinn Sgritheall (just North of the Knoydart peninsula).

Granite
Locations : Cornwall, Devon, Cairngorms, Red Cuillin
Granite is formed by molten rock cooling slowly underground. It tends to form rounded mountains which are prone to weathering. The sample on the left came from Brown Willy in Cornwall (no sniggering please - its cornish for high point); whilst the sample on the right came from Scotland.

Schist
Locations : Scottish Highlands
Schist and quartzite make up quite a lot of the Scottish Highlands. This metamorphic rock is formed by compression of other rocks, thus forming flat layers. Its distinctive metallic shine comes from the layers of mica - which are either complete layers or flecks (as in the two sample here). Because this rock forms layers, it tends to make some pretty jagged ridges when it gets folded. some excellent examples of Schist landscape are the Devils Ridge in Glen Nevis and The Cobbler - both places to avoid if you have vertigo.

Garnet
Locations : Knoydart
The contorted rocks of Knoydart are full of minute burgundy coloured garnets (shown here magnified). Sizeable stones are semi-precious, being of use in jewelery. These specimens were extracted from a rotten schist, and are themselves fragile and rather small (I've magnified them for you). Note that since schists are metamorphic, these must be too.

Gneiss
Locations : Outer Hebrides & NW Scotland
This is Lewisian Gneiss. It comes in many different colours, from black to near white, with many pink banded varieties. All have the contorted streaks of this ancient squashed rock. Much of it is around 3000 million years old.
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