Metamorphic Rocks

This page is about metamorphic rocks: these are the sort of rocks which form when heat and pressure are applied to igneous or sedimentary rock, compressing and compacting the existing rock and turning it into the significantly denser metamorphic rock.

The Creation of Metamorphic Rocks:
The process these rocks go through is referred to as 'metamorphism' which means 'change in form'. Much like a caterpillar transforming into a butterfly, metamorphic rocks go from one type of thing to another. The changes can come about simply by the rock being deep under the surface of the earth and so subjected to extreme temperatures and high pressure: however, metamorphic rock can also be formed from the stress of tectonic processes (from Earth's plates colliding together).

Where Can Metamorphic Rock Be Found?
Metamorphic rock is quite common throughout the world as it comprises most of the Earth's crust.
There are a few types of rock which can be found in Tasmania
- Slate, found near Pipers River
- Quartzite, found in most of SW Tasmania
- Schist, found near Strathgordon

Types of Metamorphic Rock:

There are quite a few different types of metamorphic rock: marble (essentially compressed limestone or dolomite), gneiss (originally granite) and quartzite (compacted sandstone), to name a few. Here is a photo which might help you to put things into perspective: it displays a piece of granite next to a piece of gneiss, showing the contrast between the two.

How Can You Recognise Metamorphic Rocks?

Metamorphic rocks are a fascinating type of rock, but for all of this fascination-ness they can be a little difficult to identify. 

Because of the harsh processes that metamorphic rocks go through to earn their name, the grains of this rock are packed tightly together. This means that metamorphic rocks are generally quite strong.

Also as a result of metamorphism, the crystals of metamorphic rocks become arranged into often visible layers. Slate is a common example of this, and it is considered to be good for tiling roofs and floors because of this trait. Its layers can be separated into sheets, making it easy to cut and shape while still being a strong rock.

Metamorphic rocks can, in fact, contain fossils if the rock was originally of the sedimentary variety. Due to the intense compression they undergo, the fossils tend to be noticeably misshapen.

Uses for metamorphic rock: 

Many metamorphic rocks (because of their toughness) are suited to use in construction work. Being both pretty and solid, metamorphic rock is often found to contain semiprecious stones like garnets, lapis lazuli, diamonds, rubies, jade, sapphires and turquoise. Marble is a popular metamorphic rock, often used to create sculptures and used in building for walls and floors. Quartzite, a metamorphic rock, is used for making glass because of its high content in silica.