More... Mohs Hardness Scale

When designing a seal intended for excluding (preventing the ingression of) particulate matter, we carefully examine the nature of the contaminant particles. A helpful reference is the Mohs value of particles. Mohs values refer to the Mohs Hardness Scale, a 10-point qualitative scale that ranks minerals by their relative resistance to scratching. Developed by mineralogist Friedrich Mohs, the scale assigns values from 1 (softest, like talc) to 10 (hardest, like diamond). For example, a mineral with a Mohs hardness of 7, such as quartz, can scratch any mineral with a value lower than 7, but can be scratched by any mineral with a value higher than 7. 

Here is a list of the ten index minerals on the Mohs scale, ranging from low to high on the Mohs Hardness Scale:

• Talc

• Gypsum

• Calcite

• Fluorite

• Apatite

• Orthoclase feldspar

• Quartz

• Topaz

• Corundum: (includes ruby and sapphire)

• Diamond

We'd like to recommend...

The above description begs the question, how does the hardness of a mineral contaminant relate to the hardness, or resistance to scratching, of the metals we use to build our mechanical systems? This is where the skill of our engineering staff comes into play. And we'd be very pleased to work with you, through our design process which takes contaminant hardness into account when selecting materials for exclusion seal construction, as well as in making suggestions on rod and bore specifications. 

We'd like to share an excellent resources we use to (partly) answer this  question.

The article: Mohs scale - Understanding metal hardness and mineral hardness, Published: 03/07/2025, by Paul McFadyen

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https://www.metals4u.co.uk/blog/hardness-scale-of-metals