The Rockery - Volcanic Rocks
Richards Mountain Pages

All the rocks on this page have been ejected from volcanos. They are formed either from lava flows, or from settled ash. The main volcanic areas of Britain have all but eroded away since the last eruption (millions of years ago), so I've had to cheat a bit and get some more recent rock from Iceland for some of the samples.

If you were expecting to see some serpentine here Click here instead. I gave it its own page as it comes in so many different styles.

Gabbro Locations : Black Cuillin - Isle Of Skye This piece came from Garbh Bheinn (rough hill) - an aptly named mountain, since the gabbro its is made from is extremely rough and grippy. This stuff is quite definitely volcanic, and not to be argued with, though it is superb for climbing on. Its composition is similar to basalt, but its slower cooling leads it to develop crystals (as seen shining on the piece on the right).

Lava Locations : Iceland Unfortunately the only lava to be found in Britain is in the form of cooled basalt. To get samples of interesting bubbly stuff like this you need to go a bit further afield. These particular bits came from old and new(ish) lava flows in Iceland - a country with more than its fair share of the stuff.

Smokey Quartz
Locations : Scotland - mainly the Cairngorms
This semi precious form of quartz is quite rare. The scottish variety is known as Cairngorm, after the region in which it tends to be found. However this piece was picked from the shores of the Outer Hebrides.

Tuff
Locations : Lake District, Glen Coe
You'll find this stuff scattered around the Lake District, particularly the Eastern Fells. The area was once a volcano which ejected layers of ash. The ash solidified keeping the layering and forming the tuff you see here. The centre of the volcano was somewhere near Glaramara. There's nothing much left to show for it now though. The Glen Coe variety tends to consist of rectangular specks embedded in darker rock.

Pumice
Locations : Iceland
To my knowledge there is no native pumice in Britain. This rock is ejected from volcanos with a lot of gas in it. It sets with the gas still locked in, and so forms a really light weight rock. The easiest way to identify it is to drop a piece in a glass of water. The trapped gas bubbles make it float. This sample came from around Hekla in Iceland.


Obsidian
Locations : Iceland
Obsidian is a black natural glass formed from molten silicates that cool rapidly. I am not aware of any deposits in Britain, but it volcanic past may be hiding some somewhere. This rock is lighter than expected, and could easily be mistaken for a blob of plastic waste. Thanks to Gavin for finding this specimen in Iceland.


Basalt
Locations : Skye, Snowdonia, and many other places
Basalt is the bog standard rock of volcanic eruptions. It is fast cooled, and so has no crystals, its just a uniform dull mass. This particular piece had gas bubbles, which later filled with minerals, creating the crystal filled voids. It can also form the familiar 'organ pipes' that can be found at Fingals Cave, the Giants Causeway, Svartifoss (Iceland), and to a lesser extent on Snowdon.


Diorite
Locations : skye
Diorite is a fairly rare volcanic rock. This particular piece was found on the beach at Glen Brittle, having been washed down from an unseen vein somewhere on the Cuillin. Its green colour comes from the high proportion of green Olivine bound by lighter materials.

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