the Mohs Scale (pronounced Moze) is named after minerologist Frederich Mohs. Introduced in 1822 it is a scale of mineral hardness based on the extent to which one mineral can scratch another.
Rocks are made up of more than one mineral and each mineral has a different level of hardness and durability from the other. The harder the mineral is, the stronger the bond between the atoms it is made up of are. Interestingly diamond and graphite are both made of the same element (carbon) but it is the way in which the atoms are bonded together that creates their difference in hardness.
Talc is the softest mineral and diamond is the hardest. Whilst the scale places a mineral on each number from 1 to 10 the difference in hardness between minerals is not even. As the diagram below shows, diamond is substantially harder than corrundum even though it is only one number below diamond which is a scored as 10.
The mohs scale has helped us to understand which stones are more durable than others and how we should use them in jewellery.