Canadian Rockhound: How to tell minerals apart

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Mohs Scale Minerals:
Talc
1 Talc
Gypsum
2 Gypsum
Calcite
3 Calcite

4 Fluorite
Apatite
5 Apatite

6 Orthoclase
Quartz
7 Quartz
Topaz
8 Topaz

9 Corundum
Diamond
10 Diamond

Between 2500 and 3000 minerals have been identified, but there are only 60 that you will come across in the field. They are identified by their various characteristics – colour, luster, streak and hardness are the obvious ones.

Colour

Colour is an important key to identifying your specimen – just as its important to be able to tell an apple from a pear.

Luster

Another important thing to notice when identifying a mineral is the shine – known as luster – whether it looks like metal (metallic) or glass, like diamond or silky.

Streak

The streak made by a mineral is often a different colour than the mineral itself. The streak is found by rubbing the mineral on an unglazed piece of ceramic tile. The colour of the streak is important in helping you identify the mineral.

Hardness

Another important factor in knowing your rocks is the hardness. A common system of measuring hardness is the Mohs Scale. The scale runs fron the softest mineral, talc, as "Mohs 1" to the hardest mineral, diamond, as "Mohs 10". (The pictures to the right show what these minerals look like).

The Mohs Scale:

Talc
Gypsum
Calcite
Flourite
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond

In the beginning you can use four categories of hardness:

softer than 2.5
between 2.5 and 5.5
between 5.5 and 7 and
harder than 7

Your fingernail has a hardness of 2.5. If you can scratch your mineral or rock with your fingernail, you know it is softer than 2.5. A pocket knife has a hardness of 5.5 and quartz has a hardness of 7. If you can scratch it with your pocket knife, you know it is softer than 5.5.

These four tests – colour, luster, streak and hardness – will go a long way to help you identify the mineral you find. All the mineral field guide books around the world use these characteristics in describing minerals.

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Contents:

Colour

Luster

Streak

Hardness