|
In this example, the first test performed was
hardness which is a mineral’s resistance to scratching. If steel can
scratch it, you can eliminate quartz. If the steel knife can’t scratch
it, it probably is quartz. Mineral hardness is rated from 1 (soft) to 10
(hard) on the Mohs hardness scale. Most geologists use common
objects such as a steel knife to determine the hardness of minerals.
Steel has a Mohs hardness of 5.5. If a mineral is scratched by a knife,
it is softer than 5.5. If the mineral scratches the knife, it is harder
than 5.5.
Each number on the Mohs scale has a specific
mineral associated with it. For example, talc has a hardness of 1, while
diamond’s hardness is 10.
|
Hardness |
Reference Mineral |
Common Object |
|
1 |
Talc |
|
|
2 |
Gypsum |
Fingernail (about 2.5) |
|
3 |
Calcite |
|
|
4 |
Fluorite |
|
|
5 |
Apatite |
Steel Knife (about 5.5) |
|
6 |
Feldspar |
|
|
7 |
Quartz |
|
|
8 |
Topaz |
|
|
9 |
Corundum |
|
|
10 |
Diamond |
|
|
Talc, Ropes Mine, Michigan can be scratched with a fingernail.
|
