Rocks are made up of one or more than one minerals. These minerals are inorganic, solid and pure materials that are found in the crust of the Earth and are composed of one or more elements.
While we talk about the elements, they are naturally occurring and most basic substances found on Earth and cannot be broken down.
Physical properties of minerals
There are various minerals found on the crust of the Earth, and all of them have different physical properties and chemical compositions that are unique to that specific mineral.
With the variation in the number of minerals in each rock, the chemical and physical properties of each rock differ even if they share the same mineral ingredients.
Also, the processes used for the rocks by which they are formed, such as being doughy and burned etc. makes a difference between various kinds of rocks.
However, there are a few minerals that commonly form the rock such as Quartz, mica, feldspar, hornblende and calcite.
Which rocks are more valuable?
The value of each mineral varies depending upon its significance.
The more valuable mineral is the one that is rare. Same goes for the use of minerals as the more they are used for different things, the more that mineral becomes valuable.
There are a number of minerals that are considered valuable for their beautiful properties and are used to serve various purposes such as mining platinum, gold and diamond etc.
Hardness of rocks
The hardness of rocks depends on the quantity and type of the mineral constituents of the rock as well as the bond strength existing between mineral grains.
The hardness of rocks is all about measuring the strength of bonds between atoms and the resistance of minerals to scratching instead of referring to how easily the mineral is broken.
A scratch is a permanent groove or line into the material surface being tested.
Why determining the hardness of rocks is important?
The hardness of the rock plays a vital role in determining its strength, toughness and durability.
There are generally three forms of rocks that include igneous, metamorphic and sedimentary rocks. All of these rocks are essential for our everyday life and can be used for multiple purposes.
They are used for constructing buildings, stone walls, walkways, art jewelry and much more.
Engineers and scientist lookout for the best rocks by determining their hardness so that they identify the ideal ones for their relevant needs.
By assessing the hardness of rocks, they’ll be able to recognize the best quality rocks and use them for various purposes.
Commonly used hardness test
The common method used to test the hardness of minerals was developed by a German mineralogist named “Friedrich Mohs” in 1822. A hardness scale was developed by him to identify the properties of minerals.
The hardness scale is called as “Moh’s scale” and consist of numerical mineral values of hardness ranging from 1-10.
The softest mineral on the list is talc and is given the least hardness whereas diamond is given the highest hardness rating rendering it to be the hardest mineral.
How to test the hardness of rocks at home?
Even though Moh’s test is globally used and appreciated a reliable method for testing the accurate hardness of rocks/minerals.There are a number of household objects or materials that can be used to test the hardness of rocks at home because they have the hardness identical to the ones used in Moh’s hardness test scale.
|Glass plate (window glass)||5.5|
|Steel file (chain saw file)||6.5|
For determining the hardness of the unknown rock, it is relatively easy to use the objects mentioned in the table since the majority of the minerals have the hardness between 2 and 7.
You should scratch the rock against the substance to measure the hardness of rock. If both of them scratch each other, it means they both have equal hardness. Let’s elaborate on this discussion in detail.
The material you are going to take to test the hardness of the rock includes glass plate, copper penny, steel file, pocket knife, one piece each of Quartz and fingernail.
These materials are easily available in the home hence making your hardness testing easier.
You can simply begin by scratching the above-mentioned household objects against the mineral/rock to be determined for hardness.
You begin with the soft objects such as fingernail with the hardness of 2. Scratch the fingernail against the mineral to be observed.
If the fingernail scratches the mineral, the mineral is then expected to have a hardness of less than 2. You can continue using different household objects to check the relevant hardness of minerals afterwards.
However, if you are able to scratch the mineral against the objects having higher hardness such as glass plate, it means the hardness of the mineral is greater than 5.5.
Special safety procedures
Glass plates, Quartz and pocket knives specimens can be very sharp, so you should be very cautious while using them. You should take preventive measures and use them carefully, so you don’t cut yourself.
A great way to carry the procedure of hardness testing is to place the specimen on a stable work surface first. Then, hold it steady and make an attempt to scratch it while testing implement.
We use various characteristics to identify people such as hair color, language, eye color etc. Similarly, geologists use specific characteristics to identify minerals and rocks.
Engineers, scientists and builders etc. also emphasized on determining the hardness of these rocks before making them into use. Instead of getting into extensive hardness testing procedures, people can simply use household items and determine the hardness of minerals and rocks.
This home-based procedure can be very beneficial either you are teaching your kids the science projects or merely using it for your personal projects.