About the rocks in the Arctic Garden

The rocks are the property of the Geological Survey of Finland. Geology is the study of rocks and how they are formed. ‘Mente et malleo’ – with mind and hammer – is the traditional slogan of geologists. Rock samples are collected from nature and analysed in laboratories.

Diverse chunks

Get familiar with some geological concepts:

• Bedrock is composed of rock types. In Finland, the bedrock is often covered by soil, or to be more precise, by different soil types.
• Rock types are composed of either a single mineral or several minerals.
• Minerals are crystalline materials. The most typical minerals in rocks are quartz, feldspar and mica.
• Ore minerals are minerals that can be used to make metal.
• Soil types are either composed of minerals and rock types (such as sand or clay), or they can be organic (peat and mull).

Rock types are classified into three major categories based on how they formed:

• Igneous rocks are formed when molten rock – magma – cools, crystallises and hardens.
• Sedimentary rocks are formed when loose soil types are re-deposited and hardened.
• Metamorphic rocks are formed over millions of years as igneous or sedimentary rocks crystallise again due to high pressure and temperature changes. Metamorphic rocks can undergo metamorphism more than once.

Find the boulders

In more detailed classifications, rock types are named based on their structure and mineral composition. For example, igneous rocks are classified into intrusive, volcanic and dike rocks. They differ from each other based on their look and structure, but their mineral composition may be the same.

We have plenty of rock types that are of volcanic origin – in other words, igneous rocks – that have undergone varying degrees of metamorphism. Finland has a lot of metamorphic rocks, as does this exhibition.