What is the difference between a rock and a mineral?

How it works

Inside every mineral, tiny particles called atoms line up in a neat, repeating pattern called a crystal structure. That pattern helps decide how hard, shiny or colourful the mineral is. Diamond and graphite are both made of carbon, yet diamond is the hardest natural mineral while graphite is soft enough to use as pencil 'lead'.

A rock is more like a fruit salad. Look closely at granite and you can often spot glassy grey quartz, pale pink or white feldspar and flakes of shiny black mica. Some rocks are mostly one mineral: marble, for example, is mainly calcite.

Geologists sort rocks into three big families by how they formed. Igneous rocks cool from melted rock, sedimentary rocks build up from layers of sand and mud, and metamorphic rocks are older rocks changed by heat and pressure. The minerals inside are clues to a rock's life story.

Where to see it in New Zealand

The South Island's Māori name, Te Waipounamu, refers to the waters of pounamu (greenstone), a treasured tough green stone found in West Coast rivers. In Auckland, Rangitoto Island is a young volcano built from dark basalt rock.

Try it together

Collect a handful of pebbles from a beach, riverbank or garden and look at them with a magnifying glass. Can you see grains of different colours, sparkly flakes or see-through bits? Sort them into groups and guess which ones contain several minerals. Go near water only with an adult.