Transcript Identifying Minerals

1. A mineral occurs naturally
2. A mineral is solid (definite shape
& volume). It’s a crystalline
structure.
3. A mineral has a definite chemical
composition (combines several
atoms).
4. A mineral’s atoms are arranged
in repeating patterns (Crystal).
5. A mineral is inorganic (was never
alive)
Magma
► Minerals
magma.
► Magma
can form from the cooling of
is molten material found beneath
Earth’s surface.
Minerals from Solution
► Minerals
solution.
► For
can form from a supersaturated
example: Gypsum deposits can form
from the evaporation of water.
Of the almost 4000 known minerals,
only about 30 are common.
The most common are
quartz,feldspar,mica, and calcite.
These rock forming minerals make
up most of the rocks found in the
Earth’s crust.
Silicates
► Minerals
that contain both O and Si and one
or more other elements are known as
silicates.
► Make
crust.
up 96% of the minerals in the Earth’s
► Example:
Feldspar and Quartz
Carbonates
► Minerals
composed of one or more metallic
elements with the carbonate compound CO3.
► Examples:
Calcite, dolomite, and
rhodochrosite.
To be able to identify these and
other minerals, we need to look at
the properties used to separate
and distinguish these minerals.
Oxides
► Compounds
of oxygen and a metal.
Minerals are identified
by several properties!
Color is the most easily observed
mineral property and the least
useful!
Some exceptions to the color rule
would be cinnabar, which is
always red, and malachite,
which is green.
Discuss the following with a
neighbor!
How many of the characteristics
of minerals can you name?
Why isn’t color a very good
property to identify most
minerals?
Luster refers to the way a
mineral shines in reflected light.
The mineral on the left has a
metallic luster, the one on the
right, a nonmetallic luster.
Streak of a mineral is the color of its
powder when rubbed on an
unglazed white tile.
The streak is often not the same
color as the mineral.
A minerals color may vary, but the
streak rarely will!
The cleavage of a mineral is its
tendency to split easily or to
separate along flat surfaces.
Cleavage can even be observed on
tiny mineral grains making it a very
useful property!
Mica is probably the best example as
it splits into thin sheets. It is said
to have one perfect cleavage.
Feldspar splits readily in two
directions, always at or near right
angles.
Not all minerals show cleavage.
Those that don’t break along cleavage
surfaces are said to have fracture.
Discuss the following with a
neighbor!
There are four common minerals,
how many can you name?
Of the four common minerals,
which one makes up over 60% of
the Earth’s crust?
The hardness of a mineral is its
resistance to being scratched.
Diamond is the hardest of all
minerals, and talc is the softest.
Friedrich Mohs devised a hardness
scale.
In this scale, ten well known
minerals are given numbers from
one to ten.
Lets take a look at the ten minerals
used and some of the simple tests.
The Mohs Hardness scale ranks from
most likely to be scratched (1) to
least likely to be scratched (10).
Crystal shape can be a useful
property to identify minerals if the
minerals have had the time and
space to form crystals. Most
mineral grains that are found in
rocks, lack the room to grow.
Specific gravity tells you how many
times as dense as water the
mineral is.
Pure gold can have a specific gravity
as high as 19.3!
Calcite is calcium carbonate, CaCO3.
If a drop of weak hydrochloric acid
is placed on calcite, the acid
bubbles as carbon dioxide is
released.
Minerals that can be hammered thin
or shaped are said to show these
properties.
Can you think of a mineral that
might be shaped or hammered?
Gold would be a perfect example!
Halite (rock salt)
can be identified
by its taste.
This practice is not
recommended!
Ores
►A
mineral is an ore if it contains a useful
substance that can be mined at a profit.
► Look
around the room, are any items made
of iron? If so, their original source may
have been hematite.
Items that contain iron
Ores Continued…
► Ores
located deep with Earth’s crust are
removed by underground mining.
► Ores
that are near Earth’s surface are
obtained from large, open-pit mines.
Gems
► What
mica?
makes a ruby more valuable than
► Rubies
are much rarer and more visually
pleasing than mica.
► Rubies
► Gems
thus are considered GEMS.
are valuable minerals that are prized
for their rarity and beauty.
Examples of Gems
Diamonds
Emeralds