Name
Class
Date
Identification of Minerals Activity: Hardness
Background Information: The hardness of a mineral sample is a useful characteristic to aid in
identification of minerals. Moh’s Table of Mineral Hardness measures the “scratchability of a
substance on a scale of 1 to 10 with 10 being the hardest (diamond) and 1 being the softest
(talc). A harder mineral will scratch a softer mineral. A softer mineral will leave a mark
(pulverized mineral) on a harder mineral. Certain substances have a known hardness and are
used as comparisons to help identify the hardness of other minerals.
Below is Moh’s Table of Mineral Hardness.
Substance
Talc
Gypsum
Fingernail
Calcite
Penny
Fluorite
Apatite
Iron nail, Glass
Feldspar
Steel file
Quartz
Topaz
Corundum
Diamond
Hardness
1
2
2.5
3
3.5
4
5
5.5
6
6.5
7
8
9
10
Objectives: To test, determine, and describe the hardness of various minerals.
To use the property of hardness to classify and identify mineral samples.
Materials: mineral samples, penny, iron nail, fingernail, glass, porcelain scratch plate, steel.
Procedure:
1. Collect mineral samples and spread them out on the lab table.
2. Test each sample for hardness. This is done by comparison. Use the items with known
hardness to compare with your samples.
3. Test each sample against several known substances.
a. For example: if a nail scratches the mineral then the mineral hardness must be less
than the 5.5 hardness of the nail, so then test with the penny to determine if the
mineral is harder or softer than the 3.5 hardness of the penny; if the sample
scratches the glass then it must be harder than the glass, so then test with the
scratch plate and see if the sample is harder or softer than the 7.0 hardness of the
scratch plate.
b. You may also compare one mineral sample to another mineral sample that you
know the hardness of.
4. Record your results and be sure to describe how you determined the hardness.
5. Answer discussion questions.
6. Use the Mineral Identification Key to try and determine the name of your sample.
Data:
Sample #,
Name
1
Hardness
How Hardness Was Determined
2
3
4
5
6
7
8
9
10
11
12
13
Discussion Questions:
1. Was it more difficult to determine the hardness of some samples than it was for others?
Explain.
2. Why would the hardness of a mineral not be considered an exact value?
3. How do you think it would be possible for two samples of the same mineral to have
different hardness values?
4. Why would knowing the hardness of a mineral be useful information?