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Identifying metals

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Mineral Identification

There are over 4000 different minerals.

 Some of them are instantly recognisable, but many can look very similar. So how do you tell them apart?

There are a few tests that you can do to find out a minerals identity.

Minerals with distinctive colours

Some minerals exhibit particular colours that make them easier to recognise.

Yellows and golds examples	Reds and oranges examples	Purples and blues examples	Greens examples
Gold: gold, pyrite, chalcopyrite Yellow: sulphur, carnotite Yellow-green: autunite	Rose red: rhodonite Red wine: cuprite Ruby red: ruby Marmalade: citrine	Purple: amethyst Blue: azurite, lazulite Sky blue: sapphire	Opaque green: malachite, varsicite Jade green: jageite, nephrite Clear green: emerald, olivine

Mohs Scale of Hardness

The Mohs scale of hardness was created by Friedrich Mohs a German mineralogist in 1812. When mineralogists talk about hardness, they mean scratch hardness- the minerals resistance to being scratched.

The Mohs scale arranges minerals from 1 to 10. 1 is Talc and 10 is Diamond. Diamond is the world’s hardest mineral. In the original Mohs Scale, ten minerals were arranged in order of increasing hardness and were assigned the numbers one to ten. These ten minerals are shown here:

Mohs mineral	Mohs Number	Can be scratched by	Simple Classification
Talc	1		soft
Gypsum	2	Fingernail	soft
Calcite	3	'Copper' coin	medium
Fluorite	4	Iron nail	medium
Apatite	5	Knife blade or glass	medium
Orthoclase (feldspar)	6	penknife	hard
Quartz	7	Steel file	hard
Topaz	8	Sandpaper	hard
Corundum (emery)	9	Knife sharpener	hard
Diamond	10		hard

Glow in the Dark

Some minerals glow in the dark!   The minerals appear to glow when these different types of light are shone onto them. This glowing effect is called fluorescence. The word fluorescence is taken from the mineral fluorite, which usually glows a bright purple/blue under UV light.

 

Photograph reproduced with the kind permission of the Geevor Archive