Transcript Mohs` Hardness PPT

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Mohs Scale of Hardness
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Mohs Scale History
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Mohs scale was devised by Friedrich Mohs in
1812
You use Mohs scale by testing your unknown
mineral against these known minerals.
The known minerals are:
1. Talc
6. Orthoclase (Feldspar)
2. Gypsum
7. Quartz
3. Calcite
8. Topaz
4. Flourite
9. Corundum
5. Apatite
10. Diamond
Comparing Hardness
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Whichever mineral scratches the other
mineral is harder.
 If they both scratch each other, they are
the same hardness.
Handy Objects
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There are a few handy objects that also fit in the
Mohs scale.
 A fingernail is between 2 and 3.
 A copper strip or penny is just under 3.
 A knife blade or bar magnet is 5 to 5.5.
 Window glass is 5.5 to 6.
 Porcelain streak plate is 6.5 to 7.
Ex. If the mineral can scratch the porcelain plate
the mineral is harder than 7.
If the porcelain streak plate can scratch the mineral,
then the mineral is softer than 7.
Hints for Using the Scale
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A larger specimen will be softer than smaller
crystal specimens.
Some minerals will have a range of hardness due
to impurities.
Don’t be fooled by a dust trail on a mineral. It
may be the mineral that you scratched the new
mineral with that left some behind.
Remember this phrase to remember the minerals
on the Mohs Scale:
The Geologist Can Find An Ordinary
Quartz, (that) Tourists Call
Diamond!
If your mineral can….
Can be rubbed off with your fingers ……1
Can be scratched with your fingernails ..2
Can be scratched with a penny……….3
Can easily be scratched with a butter knife …4
Is hard to scratch with a butter knife ….5
Can be scratched with a steel nail but not glass ….6
Can be used to scratch glass or a porcelain plate …..7
Can scratch topaz …..8
Can scratch corundum ……9
Can scratch diamond …….. 10
Moh’s Mini Lab
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There are nine minerals around the room.
Your group will grab a mineral kit and you
will move around the room testing the
hardness of each mineral.
 When you have the minerals hardness
determined, get the actual mineral names
from the teacher.
 Check online for the actual mineral
hardness and answer the questions.