Back

MINERALS
Lesson 1 - Page 5

Next 

In this example, the first test performed was hardness which is a mineralís resistance to scratching. If steel can scratch it, you can eliminate quartz. If the steel knife canít 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 diamondís 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.


   Back

[Back to Minerals]   [Earth Science Grid]

Next