Hello! My name is Garrett Barmore.
I'm the curator here at the
W. M. Keck Earth Science and Mineral Engineering Museum.
And welcome to Mineral Monday.
Let's see what I have in store for you today.
[Mineral Monday with Garrett Barmore]
[Thank you to our sponsor, Newmont.]
Today we're talking about the Mohs Hardness Scale.
The Moh's Hardness Scale was developed
by Friedrich Mohs, who was a mineralogist
in the early 19th century.
He developed it in 1812.
And what the Mohs Hardness Scale is
it is just a way to determine the hardness
of rocks and minerals.
It is a bit arbitrary, 
but it is widely used.
And the classic minerals that 
Friedrich Mohs picked are
talc,
gypsum,
calcite,
fluorite,
apatite,
orthoclase,
quartz,
topaz,
corundum,
and then diamond.
And we don't have diamond out today.
And this goes from 1 to 10,
talc being the softest
and diamond being the hardest.
So, if topaz cuts something
then that means it is softer than an 8
on the hardness scale –
topaz being an 8.
Your fingernail, for example,
is about 2.5 on the hardness scale.
So if you can scratch it with a fingernail
then it is softer than a 2.5.
This is one of the first steps to use
when trying to classify 
or figure out what your rock or mineral is.
If you would like to see our display on the Mohs Hardness Scale,
you can see it in case 1 on the main floor of the main gallery.
And I'll see you next Mineral Monday.
