Is It a 1 or Is It a 10? Mohs Scale of Hardness

When I taught 6th grade science, the Mohs Scale of Hardness is a concept the students learned in my "Rock with Science" section.  That's when the students would go around muttering "Sedimentary, my dear Watson!  Sedimentary!" as they scratched different mineral samples with different instruments/other samples.  For those that aren't science geeks, what is the Mohs Scale of Hardness?  And why should you care?  The principles of the scale matters in everyday life, from something as simple as abrasives for cleaning a sink to high tech gadgets to satellites in outer space.

Courtesy of Ossola Minerals

Wealthy Viennese banker Jacob Friedrich van der Null bought eleven of Europe's top mineral collections in 1802 and ended up with almost 4,000 specimens.  He wanted his new collection to be classified and catalogued and hired a young German mineralogist, Friedrich Mohs, to make sense of the collection.  For the next 10 years, Mohs conducted many tests on the minerals, such as specific gravity, brittleness, the ability of the mineral to conduct electricity, etc.  He puzzled for a long time, however, how to quantify the absolute hardness of the many minerals in the collection.  

Mineral poster courtesy of Feenixx Publishing

In a stroke of genius, Mohs developed a comparative scale instead.  The scale is based on the resistance of a harder mineral to not be scratched by a softer mineral.  He chose ten minerals "of which every preceding one is scratched by that which follows it" and assigned a number, from 1 to 10.  Talc is the softness at 1 and diamonds are the hardest at 10 (although there are some manmade diamond nanorods that are harder than a 10 now).  All other minerals fall between the numbers.  The scale is somewhat arbitrary since Mohs used minerals that were easily available to him.  There are other scales of hardness, such Rockwell, Vickers, and Brinell, but the The Mohs Scale of Hardness is probably the most commonly used scale to this day.   

Below is a chart that shows the Mohs scale, courtesy of Indiana Geological Survey 

   

The Mohs Scale of Hardness is should always be considered by jewelry makers  as they choose gemstones for specific projects.  Gemstones that are softer are best not used for rings and bracelets, pieces of jewelry that can get a lot of unintentional abuse from wearing.  They survive much better used in necklaces and earrings.  I had a beautiful pearl ring at one time that, through constant wearing, lost a lot of its lustrous nacre and actually became somewhat flattened on one side!  The flatness was caused by using the stair bannister when climbing up and down our stairs and unknowing lightly scraping the ring on the wall many, many times!  Many old amber rings have surfaces that look somewhat cloudy due to a countless number of microscopic (or not so microscopic!) scratches.  All fine jewelry needs to be cared for, but those with softer stones need extra care.

Here's another chart that shows some of the more common gemstones that are used for jewelry making, courtesy of Ann Vogt Jewelry

I thought it would be fun to share items from ArtFire studios that represent the Mohs Scale of Hardness.  To tell the truth, I wasn't sure I would find everything, but came away very pleased and excited.  Here is the Mohs Scale of Hardness ArtFire style:    

Vintage Avon perfumed talc from Lisa of  SomebodyStopMeVintage

Ancient Bactrian carved gypsum seal by Anna of CraftsofthePast

#3 - CALCITE 

Yellow calcite and black onyx bracelet by Diana of NightMaiden

AAA quartz nuggets and amethyst necklace by Catherine of ShadowDogDesigns

London blue topaz and blue diamond ring by Marge of MaggieMays

Natural ruby and coin pearl earrings by Simona of adora_by_simona

Rough diamond set in a sterling silver band by Lynda of WestWindCreations

So, there you have it - the Mohs Scale of Hardness.  I hope you enjoyed the post and looking at the beauties featured.  If you would like to make my days, please leave a comment (: