Mr. Mohs
Tim Griffin

Mr. Mohs
by Tim Griffin, 2023
No recording yet.
12-bar blues (plus two short bridges) with heavy bass groove, a la Stevie Ray Vaughan

Mohs was a geologist who made up a scale
For identifying minerals, his scale will seldom fail
When you grapple with a sample, here’s a simple test that he proposed
When you want to know the hardness, just ask Mr. Mohs

Talc is pretty soft, so he started there and then
He organized the minerals on a scale from one to ten
One is the softest, ten is as hard as it goes
When you want to know the hardness, just ask Mr. Mohs

(bridge) You can memorize the minerals if you read and review
Talc is number one and gypsum number two
Number three is calcite, fluorite’s number four
Number five’s your apatite, your appetite for more!

Want a way to measure the hardness of a thing?
To check if it’s a diamond in the center of a ring?
You can test it by scratching with any simple substance that you know
When you want to know the hardness, just ask Mr. Mohs

(bridge) Six is orthoclase feldspar, say that three times fast
Seven is a quartz, of course, and eight is topaz
Nine is a corundum and a diamond a ten
If you want to memorize ‘em all, I’ll sing ‘em all again

Rocks are combinations but minerals are pure
The hardness is a fine way to identify for sure
The scratch test is best for mineral composition to disclose
When you want to know the hardness, just ask Mr. Mohs

To identify by hardness, just ask Mr. Mohs!


Many minerals look alike. For example, quartz and calcite can easily be mistaken for each other and an uncut diamond looks a lot like both. This can make work difficult for a geologist. In 1812, the geologist Friedrich Mohs came up with an easy way to test minerals by hardness rather than by appearance.

How The Mohs Test Works
We've known for a long time that some minerals are harder than others, and that a harder mineral will scratch a softer one when we rub two minerals together. Mohs' big idea was to take ten well-known minerals and arrange them by hardness on a scale from 1 (talc) to 10 (diamond). If you carry a sample of each of these minerals with you, you can test any new substance you find by trying to scratch it with each of your ten known minerals. For example, suppose you are out hiking and you find a stone that looks like a garnet. If you can scratch your mystery stone with a topaz (hardness 8) but not with a quartz (hardness 7), this would confirm that your sample may be a garnet. Of course, it will only work if you also know that a garnet has a hardness of 7.5 but that's what a field guide to rocks and minerals is for; and of course you also carry one of those when you go hiking, right?

Further tests will still need to be done when you get back to the lab before you can be sure your sample is definitely a garnet (there are other substances between 7 and 8 on the scale) but the Mohs scale is still a great field test for identifying minerals.

Note To Teachers
Aside from the specific content and vocabulary of this song, the Mohs scale can be used to develop the bigger idea that science is about the organized and methodical study of the world around us; and that we can find patterns in nature to help us understand and predict natural phenomena. Plus it's fun to go outside and play with rocks.

Here are some academic content standards addressed by this song.

Fifth Grade
NGSS.5-PS1-3. Make observations and measurements to identify materials based on their properties.
NGSS.PS1.A: Structure and Properties of Matter. Measurements of a variety of properties can be used to identify materials.
CC.MP.2. Reason abstractly and quantitatively.

Middle School
NGSS.MS-ESS2-3. Analyze and interpret data on the distribution of fossils and rocks, continental shapes, and seafloor structures to provide evidence of the past plate motions.
NGSS.MS-ESS3-1. Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes.
RST.6-8.3. Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
CC.MP.2. Reason abstractly and quantitatively.