Transcript Minerals

Minerals
6.E.2.3 Explain how the formation of soil is
related to the parent rock type and the
environment in which it develops.
Properties of Minerals
• What is a mineral?
– Naturally occurring
– Inorganic
– Solid
– Crystal structure
– Definite chemical composition
Where are minerals found?
Naturally Occurring
• A naturally occurring substance is one that
occurs in the natural world
• Materials made by people are NOT
minerals
• Would a cubic zirconia be considered a mineral?
Inorganic
• Minerals cannot form from materials that
were once part of living things
• For example: Coal
– What is coal formed from?
– Is it considered a mineral?
– Would a bone be considered a mineral?
Solid
• Minerals are solids
• What are the particles of a solid like compared to
those of a liquid or gas?
• A solid has a definite volume and shape
Crystal Structure
• Minerals have a crystal structure
• Crystals have flat sides, called faces, that
meet at sharp edges and corners
• The particles of minerals line up in a
pattern that repeats over and over again
• How does this repeating pattern affect the shape of
the mineral?
Crystal Structure
Crystal Structure
Definite Chemical Composition
• A mineral always contains certain
elements in definite proportions
• Almost all minerals are compounds
• What is a compound?
• Some minerals occur in their pure form
– Copper, silver, gold
• These minerals would also be considered what?
Chemical Composition
Identifying Minerals
• Geologists have identified about 3,800
minerals
• Each mineral has characteristic properties
that can be observed simply by looking at
the sample
• Other properties must be tested
Identifying Minerals
• Color
• An easily observed characteristic
• Color alone is often too little information to identify
a mineral
Identifying Minerals
• Streak
• The color of a mineral’s powder
• Streak and color are often different
• Streak test= rubbing a mineral on an unglazed
ceramic tile
Identifying Minerals
• Luster
• Term used to describe how light is reflected from a
mineral’s surface
– Metallic, glass, waxy, greasy, pearly, submetallic or dull,
silky, and earthy
Metallic
Glassy
Earthy
Identifying Minerals
• Density
• Each mineral has a characteristic density
• Density is the mass in a given space
– Mass per unit volume
Identifying Minerals
• Hardness
• Determined using Moh’s Hardness Scale
• Determined by scratch test
Identifying Minerals
• Crystal Systems
• Crystals of each mineral grows atom by atom to
form that mineral’s particular crystal structure
• Geologists classify these structures into six groups
• Sometimes the crystal structure is obvious from
the mineral’s appearance
• Sometimes the crystal structure is only visible
under a microscope
• A few minerals are still considered minerals even
though their particles are not arranged in a crystal
structure
Identifying Minerals
• Cleavage
• A mineral that splits easily along a flat surface is
said to have cleavage
Identifying Minerals
• Fracture
• Most minerals do not split evenly
• Minerals that break apart in an irregular way are
described in terms of fracture
– Types of Fracture:
• Curved, shell-like surface, hackly fracture – rough,
irregular surfaces
Identifying Minerals
• Special Properties
• Fluorescence, reactivity, magnetism, optical, and
electrical
How Minerals Form
• What is a geode?
– A geode is a rounded, hollow rock that is
often lined with mineral crystals.
How Minerals Form
• How does a geode form?
– Crystals form inside a geode when water
containing dissolved minerals seeps into a
crack or hollow in a rock. Slowly,
crystallization occurs.
How Minerals Form
• What is crystallization?
– Crystallization is the process by which
atoms are arranged to form a material with
a crystal structure.
How Minerals Form
•
Two ways minerals can form:
– Crystallization of magma and lava
– Crystallization of materials dissolved in
water
How Minerals Form
• Minerals from magma and lava
– Minerals form as hot magma cools inside
the crust, or as lava hardens on the
surface. When these liquids cool to a solid
state, they form crystals.
How Minerals Form
• Size – the size of the crystals depends
on several factors:
– the rate at which the magma cools
– the amount of gas the magma contains
– and the chemical composition of the
magma.
How Minerals Form
• Size of Crystals:
– Rate of cooling:
• magma that cools below the surface cools
slowly over many thousands of years
• Slow cooling leads to the formation of large
crystals.
How Minerals Form
• Size of Crystals:
– Rate of cooling:
• Magma closer to the surface cools much faster
– rapid cooling does not provide enough time for
crystals to grow large
– If magma erupts to the surface and becomes lava it
will cool quickly and form small crystals.
How Minerals Form
• Size of Crystals:
– Undisturbed: if the crystals remain
undisturbed while cooling they grow by
adding atoms according to a regular
pattern.
How Minerals Form
• Minerals from Solutions:
– Sometimes the elements and compounds
that form minerals can be dissolved in
water to form a solution.
• Solution: a mixture in which one substance is
dissolved in another.
• Solute:
How Minerals Form
• Minerals from Solutions:
– When elements and compounds that are
dissolved in water leave a solution,
crystallization occurs.
How Minerals Form
• Minerals formed by Evaporation:
– as water evaporates from a solution,
crystals form (halite, gypsum, calcite)
How Minerals Form
• Minerals from Hot Water Solutions:
– When magma heats water deep under
ground, sometimes elements and
compounds that form a mineral are
dissolved in it. As the water cools, the
elements and compounds leave the
solution and crystallize as minerals.
How Minerals Form
• Vein:
– pure metals that crystallize from hot water
solutions underground often form veins,
or narrow channels or slabs of a mineral
that is often different from the surrounding
rock. The solutions of hot water and
metals often flow through cracks within
rocks, allowing the metal to crystallize into
a vein.
Questions:
Because minerals do not come from once—
living material, they are said to be
A. crystalline.
B. solid.
C. colorful.
D. inorganic.
In a mineral, the particles line up in a
repeating pattern to form a(n)
A. element.
B. crystal.
C. mixture.
D. compound.
Which characteristic is used to determine
the color of a mineral’s powder?
A. luster
B. fracture
C. cleavage
D. streak
Which is true of all minerals?
A. They are inorganic solids.
B. They have a hardness of 4 or
greater.
C. They have a glassy luster.
D. They can scratch a penny.
The End