Mineral Prop. ppt

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Transcript Mineral Prop. ppt

In 2008, crystals up to
39 feet long were
found in a cave in
Mexico at a depth of
1000 feet. The cave is
extremely hot, with air
temperatures reaching
136 °F with 90 to 99 %
humidity. The cave is
relatively unexplored
due to these
conditions. Without
proper protection,
people can only
endure about ten
minutes of exposure at
a time. See the suits
The Earth’s crust is made up of two
• Minerals and Rocks
Rocks are
Minerals are
individual crystals
of all the same stuff
of minerals
***You should see lots of different
minerals in every single rock
Main Concept: Minerals are the
building blocks of rocks!
There are five main criteria for
something to be a mineral:
a) It must be solid
a) It must occur naturally (not man-made)
b) It is made of non-living material (never alive)
c) It has a definite chemical formula (NaCl=salt)
d) It has a crystal structure (Precious?)
***Notice how each is one single type of crystal!
• Amethyst
Where do minerals come from?
 Mineral crystals can form in two main ways:
From stuff
dissolved in liquids
(Evaporation & Hot Water)
From Cooling
molten material
Minerals & Crystals from
Magma & Lava
“Extrusive” Cooling:
Lava cools Fast
(Short Time = Small Crystals)
•Minerals form from hot magma as it
cools inside the crust, or as lava cools
on the surface.
•When these liquids cool to a solid, they
form crystals (minerals).
•Size of the crystal depends on time it
takes to freeze into a solid.
“Intrusive” Cooling:
Magma cools slowly
(Long Time = Large Crystals)
Minerals Crystal Size
When the hot material cools fast, it has
smaller crystal size. When it cools
slowly, it has large crystals.
You can see
individual crystals
in Granite
= cooled slowly
You can’t see many
individual crystals in Rhyolite
= cooled very fast
Minerals formed by Evaporation
 Some minerals form when
solutions/mixtures evaporate:
 When water evaporates, it leaves behind the
stuff that’s dissolved in it.
 The longer it takes to evaporate, the larger the
 i.e. salt & water – ocean,
 Halite, Gypsum, Calcite.
***All the white stuff = salt mineral crystals that formed
when the water of this lake evaporated.
The mineral material was left behind
These salt crystals formed from
salt water because as the water
evaporated, the salt wasn’t
dissolved anymore. So the
chemical energy in salt takes
over and crystals form.
Do you notice the characteristic
cubic crystalline shapes?
How do we
identify Minerals?
We use the different physical and chemical properties
of the mineral to identify it from other different minerals
Luster: Describes how light is reflected from a minerals surface.
Streak: Is the color of the minerals powder when dragged across a surface.
Crystal shape: Different minerals make different crystal shapes
Hardness: Hardness is determined by a “scratch test”.
Color: Every mineral has some natural color…ex: Gold, Blue, Clear…
Breakage Pattern: Minerals either cleave (flat sides) or fracture (rough edges)
-Really Shiny & Submetallic-less shiny
-Lacks a shine
More non-metallic lusters:
Dull or Earthy
Performing the streak test:
Drag the mineral across the piece of porcelain tile
and look at the (inside) powdered form of the mineral
Note: Once across is enough. Don’t saw the tile in half !
Crystal Systems:
It time allows and space is available, minerals
will grow and take on geometric shapes
Note: we have very few that exhibit these shapes due to being broken pieces
Hardness testing:
The hardness of a mineral is a way of describing
how easy or difficult it is to scratch it, ranked on a
scale of one to ten (10 is the hardest).
Always start
with the
softest tool
and stop
using the
harder tools
at the first
sign of a
Scrape the tool once across and listen for and/or feel the resistance
Breakage Pattern
Minerals will break along lines of weakness (if any) and will
assume one of several shapes. That means the minerals
cleaves. Here are three common appearances:
Basal: cleaves in one
direction into flat sheets
Right angle: cleaves in
two directions with two
flat sides
Cubic: cleaves in
three directions into
Breakage Pattern (cont’d)
Some minerals don’t have any lines of weakness
and will break with irregular, rough, or sharp edges.
This appearance is called fracture.
Hackly- irregular
Special Properties
• Some minerals display strange properties.
• These can include: Magnetism, fluorescence, and reactivity.
The particles of minerals
of this rock act like magnets
These minerals glow
in the dark.
A black light brings it out!
The minerals in
this rock react
with acid