Friedrich Mohs (1773-1839) - German geologist/mineralogist.
Mohs, studied chemistry, mathematics and physics. He started classifying minerals by their physical characteristics, in spite of their chemical composition, as it was done before. He created a hardness scale that is still used as Mohs scale of mineral hardness.
According to the scale above, the softest
material is Talc (which can be scratched with a fingernail), while the
hardest is Diamond. So, what does this mean in the real world?
A
mineral with a Mohs' hardness of 7 will scratch any mineral of the same
hardness or less, but can be scratched itself by a mineral with the
same or higher number. Diamond, having the highest number, is the
hardest gem known to man, and is used not only for beautiful jewelry,
but also in many industrial applications because of its durability.
The
most valuable gems have a hardness of 7 or more. Most highly prized
gemstones are also the hardest, like diamond, ruby, sapphire or
emerald. Usually anything below a hardness of 7 is liable to be damaged
quickly in everyday wear in jewellery.
To
give you some idea of the hardness of every day things, a fingernail
has a Mohs' hardness of 2.5, a penny is 3, a knife blade or fragment of
window glass is 5.5 - 6, while a small piece of emery cloth is between
8 and 9.
The Mohs' scale is important
to jewellers and bead artists for many reasons. It's important to know
the hardness of a stone or bead before you make a piece of jewellery with
it. Putting a soft stone bead next to a hard stone bead can cause
damage to the finished piece. Whan making jewellery with softer faceted
stones or cabs, it's important to protect the stone as best as possible
to minimize wear.
