>> Welcome back to
week 1, minerals
and geology introduction.
In this video, video
2, we are going
to start discussing minerals.
So after this video is
completed you should be able
to write the definition
of a mineral.
You should be able to list and
describe the major physical
and chemical properties
of minerals,
and then explain how these
mineral properties are tested.
So basically what's a mineral?
Well, it's an inorganic solid
that is naturally occurring.
You can look in your textbook
for a more specific definition.
I'm going to explain it in
a little bit more detail,
but that's basically
what a mineral is.
And minerals are what make
up the rocks that we're going
to be looking at in
the next two weeks.
So what are the mineral
properties?
Well, we're going to
walk through these
in a very similar way as
you are going to in lab.
So the first thing that
we'll talk about luster.
And we'll get into
color, hardness, streak,
cleavage and then some others.
So the first one, luster,
which is the way the
mineral reflects the light.
Basically what that is is your
luster can either be metallic
or non-metallic.
So basically does it
look like metal or not?
So metallic things are
going to be silver, gold,
brass, things like that.
It might help you guys to
watch the lab prep video
that I have posted
in the lab materials.
So some of the non-metallic
things
that you'll see might be earthy,
kind of a dull look
to it, powdery.
Or it might look kind of
glassy, it might be shiny.
So some students can confuse
the glassy look, the shininess
with the metallic look.
And it's very important to know
that metallic looks like metal.
That's the main thing.
Metallic, metal has
that appearance to it.
The next thing to
look at is color.
And color is something that
can be deceiving at times.
For instance, in this photograph
here these are all samples
of quartz.
Quartz can come in clear,
white, pink, purple, black.
It can come in yellow.
It can come in a lot
of different colors.
The color isn't necessarily
a distinguishing feature.
But you can look at the
shade of your mineral,
is it light or dark in color.
And that will kind of
guide you a little bit
into your identification charts.
Because some minerals are going
to only have the darker shades;
some are going to
have the lighter;
some of them might
overlap and that's okay.
Your charts are going
to have both on them.
So color, is it light in
color or dark in color?
If you want to list
out the exact color
on your sheets you can.
The next thing is hardness.
So basically you're going to
take your sample and test it
on a glass plate and also
using your fingernail.
Basically you're
seeing, alright,
is this mineral harder
or softer than glass.
Does it scratch the
glass or not?
And then is it harder or
softer than your fingernail.
So can you scratch the
mineral with your fingernail
and get bits of it
off on your finger.
Or does it destroy your
nail when you try that.
so make sure you watch the
lab prep video that will kind
of describe to you the correct
procedures to do this in lab.
The next thing you look at
is what is called streak.
And streak is the way a mineral
looks, the color it looks
like when it's powdered.
Here you can see four
different minerals
and then the corresponding
streak they each have.
So this gold one has kind of
a brownish lax gray streak.
The silver one has a red-brown
streak which is interesting.
This other silver one
has a silver streak.
This red one has a red streak.
And then this clear
one has a white streak.
Now, I did this on
the counter top here
because at the time I didn't
have the darker grayish black
colored streak plates.
In lab you guys are
going to have both.
So make sure if you try it
on the white one you
don't see streaks showing
up that doesn't mean it
doesn't have a streak.
It's either harder than the
streak plate or it's white.
So make sure you try it on
black streak plates as well.
The next thing you'll
look at is cleavage.
Cleavage is the way
a mineral breaks.
So the internal arrangement
of these minerals is set up in
such a way that there are planes
of weakness within
its structure.
And every mineral is going
to be a little different.
Some of them might have somewhat
similar ways that it's going
to break based on those
internal arrangements.
So basically you're going to
be looking at these minerals
and saying, yes, it has
really good cleavage,
I can see it, it's well defined.
Or, no, I don't really see
any cleavage in that mineral.
You can also get into detail
and talk about how many planes
of cleavage a mineral
has, the direction
that those planes
intersect with one another.
If you have questions about that
we can talk about that in lab.
It's a little tricky to talk
about in a PowerPoint so it kind
of helps to have the
minerals right in front
of you with hands on them.
You're only going to be
required to look at yes or no,
does it have cleavage or not.
And so what we look for, it's
going to help you also to look
at the lab prep videos
for this as well.
You can look for two
different things.
One, this mineral here breaks
into these nice slat sheets,
and you can see in this
picture here and also
up in this picture how the right
is reflecting off of the top
of those sheets all
at the same time.
So one thing is look
for a flat surface.
If you don't have a flat
surface that doesn't mean
that the mineral
doesn't have cleavage.
So take it in your hand, rotate
it around, try to get the light
to reflect off of the
different surfaces.
If you see one whole
side reflecting the light
at the same time like
you see here or here
in this image then that's
telling you that, yes,
that mineral does have cleavage.
And you could always have
cleavage, this has one plane,
this has two, these ones
have two, these have three.
So you can have a lot of
different planes as well.
Now, sometimes your mineral
might not be showing you
that cleavage breaking all
off in a nice flat surface.
But you'll see what
looks like little kind
of stair stepped
patterns on the mineral.
And that's a sign that, yes,
it does have cleavage as well.
And this will become a
little bit more clear
when you actually have the
minerals in your hands in lab.
The next thing to look at,
and this helps to distinguish
between the different
types of feldspar.
We've got potassium feldspar
which is this top one here.
And then we have
plagioclase feldspar
which is this bottom
one over here.
Now, plagioclase feldspar has
what are called striations.
So striations you
can only see these
when you're reflecting the
light off of a cleavage space.
And here you can see
how it kind of looks
like you've got some
parallel scratches
in the side of that mineral.
Well, they aren't
actually scratches,
it's just the way this internal
arrangement of these atoms
and molecules in this mineral
expresses it out for you to see.
So parallel lines
are only visible
when you reflect the light
off of a cleavage face.
And an exsolution lamellae
are color variations
that you can see on any side,
all over the mineral,
it doesn't matter.
You don't have to reflect
the light off of it.
They're just color variations.
So two very different things in
these two different minerals.
And this is the main way
to tell the difference
between the two of these.
In labs if you have questions
make sure you call me over.
The next thing, category
is others category.
And this includes
acid reactions.
So you'll take a little bit of
very weak hydrochloric acid.
Don't worry, it won't burn
you, but don't eat it,
don't put it in your eyes.
Be careful with it.
If you put a little drop of
it on a mineral if it starts
to effervesce and
bubble that means
that you have calcium carbonate
present in that mineral.
So this is kind of a
telltale sign for calcite.
If you have a mineral that is
magnetic and you have a magnet
that can be attracted to
it that's a telltale sign
that you have a magnetite.
You can also smell a mineral
and you can taste minerals,
but I highly discourage that.
Ask me does this mineral
taste salty or not.
And if I say yes
then you have halite.
Some of them have a
very distinctive smell,
and usually the smell
is going to be sulphur.
And the last thing is what's
called a crystal form.
Does your mineral have a very
distinguished crystal form
to it?
Does it look prismatic.
Does it have a dodecahedron
shape?
Is it boxy?
Or does it have some other
kind of geometric shape to it?
And these crystal form
you don't always see this.
Not every mineral has this.
But it happens when a mineral
has a space to actually grow.
So if there's a void space in
the rock and the mineral has
that extra room to grow in its
natural form, and you'll see
that expressed in the
mineral in some cases.
Some minerals don't
have it but some do,
and they're pretty neat.
So that kind of goes
through what minerals are,
some of the physical and
chemical properties in minerals
and then how we test
for these properties.
So I'll sign off, come back
in the next video and talk
about classifying how
minerals are formed
and what they're used for.
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