How Hard is that Rock? science experiment | Fizzics Education

How Hard is that Rock?

How Hard is that Rock?

Follow FizzicsEd 150 Science Experiments:

You will need:

Your fingernail (approx. Mohs Scale 2.5)

An old 2 cent coin or copper penny (approx. Mohs Scale 3.5)

An iron nail (approx. Mohs Scale 5.5)

A hardened steel file (approx. Mohs Scale 7)

Rock or metal samples eg. Granite, Marble, Iron, Zinc, etc

How hard is that rock Mohs Scale science experiment - materials needed
1 How hard is that rock Mohs Scale science experiment - scratching a rock with a penny

Gently scrape each rock or metal sample with the above tools.

2 How hard is that rock Mohs Scale science experiment - scratching a rock with a file

Make sure you scrape along the sample with even pressure, length and material.

3 How hard is that rock Mohs Scale science experiment - scratching a rock with a fingernail

Slowly work up Mohs scale until you find can scratch the sample, giving you an approximate hardness result.

Why Does This Happen?

Rocks differ in hardness, due to the different compounds that make up the rock.

In 1822 an Austrian geologist, Frederick Mohs, devised a scale that ranked different mineral samples for their hardness, therefore standardising the field tests done by miners across the world.

Mohs chose the following samples as standards due to their abundance and different hardness.

1 = Talc, 2 = Gypsum, 3 = Calcite, 4 = Fluorite, 5 = Apatite, 6 = Orthoclase, 7 = Quartz

8 = Topaz, 9 = Corundum, 10 = Diamond.

By having a standard scale, prospectors can more easily classify the materials they find.

Learn more!

From the rock cycle to volcano formation, we’ve got your geology unit covered!
Get in touch with FizzicsEd to find out how we can work with your class.

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