Miners also call fluorite fluorspar.

Fluorite consists of the elements calcium and fluorine.

Fluorite is found all over the world.

It is often found together with the minerals
Quartz, calcite, barite (heavy spar),
galena (lead glance), sphalerite (zinc blende)
or pyrite (fool's gold).

Fluorite is an important raw material.

It helps as a flux when melting metals.
It makes the molten metal liquid more quickly.
This saves fuel.
This is how fluorite came to be called fluorspar.

Microscopes and telescopes have fluorite lenses.
Even ultraviolet light shines through them.
Glass lenses, on the other hand, filter this light.
Because pure fluorite is rare,
huge single crystals are grown in factories.

Hydrofluoric acid is also produced from fluorite.
The acid is dangerous, but can etch glass.

Toothpaste contains fluoride.
It hardens your tooth enamel and
protects your teeth from caries and nasty cavities.

What shapes do fluorite crystals have?

Mostly cubes or octahedrons are found.
Octahedrons consist of two pyramids.

On the Mohs scale of hardness, fluorite has a hardness of 4.
Diamond has a hardness of 10,
making it the hardest mineral in the world.
Talc is very soft and has a hardness of 1.

Fluorite is harder than your fingernail.
You can't scratch it.
But it is too soft to scratch a glass plate.

If you hit a piece of fluorite with a hammer,
straight and smooth cleavage pieces are produced.
This is a typical sign of good cleavage.

Sometimes you can recognise such fissures in the crystal.
They look like cracks in glass.

The crystals of fluorite look colourless.
However, this rarely occurs in nature.
Tiny amounts of other elements colour the crystals
in all possible colours:
yellow, pink, purple, even black, green, blue or brown!
Some coloured fluorites have their own name.
The golden yellow fluorite is called honey spar,
the purple-coloured stink spar.
Rare and precious are pink fluorites.
They are only found in the Alps.

Some fluorites glow in the dark.
To do this, you have to irradiate them with ultraviolet light.
You can see how to create the glow without this light 
in our exciting experiment.
Click on the video!

Scientists call this glow luminescence.
For fluorite to glow, it needs energy.
It gets this from ultraviolet light
or through heating.

But how exactly does this work?
All atoms consist of a nucleus,
electrons orbit around it on shells.

The high-energy UV light lifts the electrons
on the outermost shell to the next higher one.
When the outer electrons fall back again,
they emit this energy in the form of light.
The mineral glows!

Does the glow stop as soon as the UV light is switched off?
Then you have seen the fluorescence.

But if you see the glow for longer,
like the hands on a kitchen clock?
Then you are seeing phosphorescence.
There is an afterglow.

Have fun with our little FluoRiddle!
If you've been paying attention,
you will quickly find the solutions.

(only in German)