Rock Cycle [More important than you think! When picking rocks for hardscapes you want to use Metamorphic rock in most cases, especially with water (so it doesn't leach anything into the water) but it is also important to know what type of rockscape your c
Lewisian Gneiss Rock, Isle of Lewis -the Geology of the Outer Hebrides is important - as the predominant rock type is a Lewisian Gneiss - a metamorphic rock which is astonishingly up to 3 billion years old, making it the oldest rock in Britain - two thirds the age of the Earth.
Disharmonic folds in gneiss. Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.
Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. It is composed primarily of amphibole and plagioclase, usually with very little quartz. The specimen shown above is about two inches (five centimeters) across.