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Mohs Scale

Created by  the  German  mineralogist Friedrich Mohs in 1832, the Mohs scale is used  to measure the hardness of minerals. Mohs based his scale on ten minerals that were available to him at the time. The hardest naturally occurring  mineral Diamond is at the top of the scale and therefore is rated 10.

Today,  it  is  possible  to  measure  the  scratch hardness  of  minerals  more  accurately  by  using an instrument invented in 1896 called a Sclerometer.  However,  the  Mohs  scale  is  still  widely adopted around the globe as an accurate measurement,  and  is  therefore  still  used  to measure the hardness of gemstone.

Whilst  many  scales  and  measurements  in  the   world  can  be  quite  complex,  the  Mohs  scale  is  incredibly  simple.  Imagine  you  have  just discovered a new mineral: if it scratches Apatite (5 on the scale) but does not scratch Orthoclase (6 on the scale), your new discovery registers a  hardness of 5.5 on the Mohs scale.

However,  due  to  the  way  the  scale  works,  it  simply ranks gems in order of their hardness.  What it does not do is tell you the difference  in hardness, i.e. how much harder a gem that  records 8 is compared to one which only reaches  6.  For  example,  Diamonds  are  presently  the  hardest known mineral (therefore being 10 on  the  scale),  and  are  approximately  four  times  harder than Sapphire which registers 9 on the  Mohs scale and 30 times harder than Apatite at number 5.

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