What is the Mohs Scale?

What is the Mohs Scale?
Spread the love

Diamonds are an incredibly strong substance. In fact, diamond is the hardest material on earth. It is so hard that is measures 10 on the Mohs Scale. This scale is used by many people in manufacturing and industry and help them to determine the best method for cutting or breaking an item. This is where mechanical items such as Tapping Machines offered by https://www.cotswold-machinery-sales.co.uk/roscamat/pneumatic-tapping-machines/roscamat-400-pneumatic-tapping-machine/ can be utilised.

The Mohs Scale is a system for rating the hardness of minerals and gemstones. This is determined by looking at how scratch-resistant a material is and how the surface of the gem or mineral reacts to a sharp point. There is another test that measures a gem’s toughness and this test consists of applying pressure to see how well it responds without chipping, breaking or developing cracks.

Image credit

The Mohs Scale was invented by Friedrich Mohs (pronounced Moze) in 1822. Mohs chose ten minerals and gave them numbers based on their reaction to being scratched by other materials. It sounds too simple but it’s a highly effective judge of hardness and so is still in use today.

The scale can be misleading for those first looking at it. The difference between substances and the number that relates to their hardness is not equally spaced on the scale. For example, on the scale diamond is only one number away from Corundum (a group of minerals including rubies and sapphires). However, in reality a diamond is many times harder than these gems.

However, the Mohs Scale is great for identifying the durability of different gems, which is crucial when it comes to deciding the best materials to be used in jewellery-making.

The scale contains 10 minerals which have been given arbitrary values of hardness. If a mineral is able to be scratched by orthoclase but not apatite, the hardness is considered to be in the middle of the scale at between 5 and 6. The scratch must be a considerable mark and not simply a chalk mark that can be rubbed off.

When a mineral is undergoing testing, it needs to be determined if it is fine-grained, pulverulent or friable. A test could simply loosen mineral grains without testing the deeper surface of the gem. Therefore, specific textures could hinder a true and trusted hardness conclusion.

Therefore, even though the Mohs Scale is ideal for identifying the hardness of minerals, it is not sufficient to gauge the hardness of industrial substances such as ceramics or steel. These materials can be tested for hardness using the Knoop or Vickers hardness test.

Image credit

A further downside to the Mohs Scale is that it does not follow a linear pattern. There is no proportional increase in hardness and the gaps that separate minerals are not equal. An example of this can be seen with the difference of levels 3 and 4 between calcite and fluorite representing a 25% increase of hardness difference between the two. However, corundum and diamond are 9 and 10 on the scale but diamond is 300% harder than the former.

Leave a Reply

Your email address will not be published. Required fields are marked *