Earth & Space
Why do rocks contain different minerals?
A rock shows different grains. Puschel explores the minerals it is made of.
The short answer
Many rocks contain different minerals: natural substances with an orderly internal structure. They combine in different ways as rocks form. The visible grains can therefore look different.
An imagined Wusel scene
Puschel and Flauschi investigate
Puschel wants to name a speckled rock from its overall colour. With Lumi, Flauschi uses a magnifier to point out light and dark grains. They draw the grains separately. He leaves its name blank: reliable identification needs more clues.
Try explaining it
Why is a rock's overall colour often not enough to identify it?
Choose a), b) or c), then explain your choice.
- a)The overall colour already uniquely describes all its components.
- b)Grains of the same colour must be the same mineral.
- c)Different components and other features need comparison.
Show the explanation
Correct: c): Different components and other features need comparison.
Many rocks contain different minerals: natural substances with an orderly internal structure. They combine in different ways as rocks form. The visible grains can therefore look different.
Word help
- mineral
- A natural substance with a particular composition and ordered internal structure.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
A rock can have many ingredients
A rock often contains different minerals. Granite, for example, can show differently looking grains.
Minerals have their own structure
A mineral has a particular composition and ordered internal structure, not readily seen as a plan with the naked eye. Different minerals give rocks different properties.
Colour is only a clue
Similar colours do not automatically mean the same mineral. Grain size and other features help specialists. An illustration cannot provide reliable identification.
Why granite shows different grains
Granite contains minerals such as quartz, feldspar and mica. Minerals are naturally occurring substances with characteristic composition and internal structure. Many grains occur together in a rock. Colour helps observation but is not sufficient for identification. Think of ingredients and a mixture: minerals are constituents and the rock is the combined material.
References for this explanation: [1]
Additional specialist reference: British Geological Survey: Gesteine und Minerale
The key points again
Discovery 1
Minerals have particular chemical compositions and ordered internal structures.
Source: [1]
Discovery 2
Many rocks contain several minerals. Different formation conditions give different compositions and textures.
Source: [1]
Discovery 3
Colour alone cannot identify a rock reliably. Grain size and other properties also give clues.
Source: [1]