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Crystals are solid materials with atoms, molecules or ions arranged in a regular structure.

Crystals usually show distinct geometrical shapes, with flat faces. Different types of atoms, molecules or ions form different arrangements that make for different geometrical shapes.

Mineral crystals are formed by a process called crystallisation.

Crystallisation can occur when:

  • a molten rock (magma) cools and solidifies.
  • chemicals in hot water react to create a solid material
  • chemical-rich water evaporates
  • the atoms in existing minerals recombine at high temperature and/or pressure

This youtube video shows spectacular images of crystals growing in a laboratory.

The liquid has lots of dissolved atoms in it (it is called a saturated solution) but crystallisation only starts when a small ‘seed’ crystal is added to the solution.

In this video there there is only one chemical dissolved in the water and all of the crystals that grow have the same shape and colour.

In a rock many minerals may crystallise at the same time and grow together.

The 3D model below shows a rock sample containing long dark crystals of the mineral amphibole that have grown together with much smaller light coloured crystals of quartz and micas.

These crystals grew when this rock was deep within the Earth and subjected to high temperature and high pressure.

Click on the image to load the 3D model. Use the mouse to zoom and rotate the model.

 

 

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A joint TESEP - AusGeol.org production.

This educational product is designed for Yr 7-10 secondary students to complement the earth and space component
of the Australian National Science Curriculum and all Australian State and Territory curricula

The content and design of this educational product is based upon materials previously published by AusGeol.org