The Softest Rock and Softest Mineral on the Earth
The softest rock on earth is sedimentary type rock and the softest mineral on earth is talc. Sedimentary rocks are known to be the softest as they are held together more loosely than metamorphic or igneous rocks. Talc is the softest mineral as it can easily be broken down to powder form.
Many tend to say a rock is a mineral and a mineral is a rock. They are indeed different but carry a very close relationship. Minerals, along with potential mineral chemical ingredients, can be contained within all three types of rocks.
Sedimentary Rocks, the Softest Rocks
Sedimentary rocks are the softest rocks you will find on earth. The softest sedimentary rocks will be the ones that did not undergo longer amounts of pressure and bonding. These sedimentary rocks can more easily be broken apart.
Igneous and metamorphic rocks have undergone large amounts of pressure, heat, and transformation. This means that the rock will be harder and more compact than softer sedimentary rock.
Many have heard of the rock cycle and there are some that have not. For a great article on the rock cycle and the changes each of the 3 types of rocks go through, see my article “Diagram of the Rock Cycle”.
Chalk is a great example of a very soft sedimentary rock. This sedimentary rock can easily be dissolved or broken apart. As you may know, chalk can be run across other surfaces and leave traces of chalk behind.
The Softest Mineral, Talc
Talc is the softest mineral known on earth. It is used on the Mohs scale of hardness as the definition for 1, being the lowest and softest on the scale. Talc is soft enough to easily be ground into powder.
Talc is considered to be a clay mineral and when in powder form will often be mixed in with corn starch to create baby powder. Other uses of talc can be found in cosmetics, paper, food, lubricants, ceramics and a quite a few others.
Talc will form from other magnesian minerals with the addition of carbon dioxide and water. This gives the term of “metamorphic mineral” to talc. Soapstone is a great example that carries larger amounts of talc within it.
Some have backed away from the use of talc as a usable product. Some researchers have suggested that talc can be dangerous enough to cause issues such as lung and ovarian cancer. Other research has found no correlation.
Talc can form by metamorphism from the mineral serpentine. The fibrous version of serpentine is quite dangerous for sure. For more information about serpentine you can read my article “All About Serpentine”. Not using talc that exists around serpentine, by my thoughts, would be a good idea.
It would seem like there are a lot of good uses for talc as we have taken advantage of the mineral. Although I do admit, it does not instill a lot of confidence when there are some instances where the use of talc could be bad.
Other Soft Minerals
With talc being the softest mineral on the Mohs scale, other soft minerals such as gypsum and calcite take up positions 2 and 3 on the same scale. Gypsum and calcite, much like talc, have carried many uses in our societies for centuries.
There are two common comparisons for the soft minerals gypsum and calcite. Gypsum is compared in hardness that is right below the hardness of your fingernail. Calcite is typically compared to just under the hardness of a copper penny
For more information on these two minerals gypsum and calcite you can read about them on these articles, “All About Gypsum” and “All About Calcite”.
Different Uses of Soft Rocks and Soft Minerals
In my research with soft rocks and soft minerals, I have noted that the uses can vary greatly with rocks and minerals that are hard.
It seems the softer rocks and softer minerals tend to have more practical everyday uses. Harder rocks and minerals seem to have more use in applications such as jewelry and display. Minerals seem to be more so in this particular observation, as harder minerals make great gemstones.
I have written several articles on various rocks and minerals in my “Rock and Mineral List”. There are several great examples of rocks and minerals describing their properties. Most rocks and minerals will include the property of hardness on the Mohs scale of hardness for your reference.
