Fluorite 1: introduction

To go directly to the unit cell structure, click the link below to page 3.

Fluorite, also known as fluorospar, is made of calcium fluoride. The mineral comes in many colours; indeed it is known as the most colourful mineral in the world. Many samples of fluorite will emit coloured light when under an ultraviolet lamp. This is called fluorescence - the word in fact comes from fluorite. Most of the elements responsible for this fluorescence in fluorite are lanthanides. Its crystals are often found as cubes.

A fragment of the bulk structure of fluorite is shown to the left. The fluoride ions are yellow and the calciums are grey. You will need to rotate the structure to see the calcium ions.

In the structure on the left the relative size of the ions is to scale, and nearest neighbour ions are virtually in contact. In future pages the ions will not be shown in contact as it obscures the internal structure of the lattice. Rather, they will be scaled to half their atomic radius, ie one eighth of their volume. In any case, the determination of ion size has its problems. What x-ray diffraction determines most accurately are the positions of the nuclei in the lattice.

Go to page 2 to look a different representation of fluorite.

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