To determine the hardness of minerals using Moh’s scale.

To determine the hardness of minerals using Moh’s scale.

STANDARDS

• To take the specimen of standard size and of regular surface, should not be less than 1 inch.
• The scratching should not be done on coated, chipped, or weathered surface as it will give inaccurate values.

THEORY:

The measure of the resistance to abrasion or scratching is known as Hardness. Materials have different hardness compared to each other. The hardness is a good test to differentiate among materials. It is the idea about how easy or difficult it is to scratch a material with another material.

The MOHs scale was invented by Fredric MOHs named after the scientist. It is the list of numbers representing hardness of materials form 1(Softest) to 10(Hardest) and these minerals are:

There are many other minerals which can also be used as indicators.

• In this practical these minerals are used as indicators on which few principles should be kept in mind that:

“That the one which scratches is harder than the one which is scratched.”

“Objects of equal hardness can be scratched with difficulty.”

“Many materials can have the same hardness.”

PROCEDURE:

1. Obtain an unknown mineral sample.
2. Arrange all the available hardness indicators in order of decreasing hardness.
3. Select a fresh surface of the unknown sample.
4. Select the hardest indicator that has not been used to test this sample.
5. Hold the sample and attempt to scratch it with a sharp point of the indicator. Press the indicator firmly but lightly against the unknown sample.
6. Inspect for an Scratched line on the sample.
7. If the sample does not show any Scratched line, the sample is harder than the indicator. Record results in the observation table and skip to procedure #8 If an Scratched line is shown the sample is softer than the indicator.
8. Generate an approximate hardness of the unknown sample.

The pictures while performing the practical are also given below for a clear demonstration.

OBSERVATION