Chapter 4 section1 what are minerals

Chapter 4: Section1
What Are Minerals?
 Minerals

–a
naturally occurring,
inorganic solid that
has a crystal
structure and a
definite chemical
composition


What 5 Characteristics Does
a Mineral Have to Have?

A mineral must be:






Naturally Occurring
Inorganic
Solid
Crystal Structure
Definite Chemical
Composition

A

What Does It Mean to Be
Naturally Occurring?

A mineral must occur

naturally

 Cement,

brick, steel, and
glass all come from
substances found in
Earth’s crust but they
are manufactured by
people


How Can Something Be Inorganic?
 Inorganic

– the mineral
cannot arise from
materials that were once
part of a living thing
 Ex. Coal is NOT a mineral
because it is made up the
remains of plants and
animals

What kind of pattern must a
mineral have?
 A mineral must have a
crystal structure – a
repeating pattern of a
mineral’s particles that
forms a solid.
 Faces – a crystal’s flat
side that meets at
sharp edges and corners


A

What kind of composition
must a mineral have?

mineral must have
a definite chemical
composition – it
always contains
certain elements in
definite proportions;
most minerals are
compounds

Cinnabar –
composed of the

elements Mercury
and Sulfur


What Is the Difference Between an
Element and a Compound?

 Element

– a substance composed of
a single kind of atom. Ex.
Hydrogen

 Compound

–

Two or more elements

combined so that the elements
no longer have distinct
properties Ex. Water H20


How Do You Identify Minerals?
 Properties:
 Density
 Crystal

Shape

 Cleavage and
Fracture
 Special
Properties

Hardness
Color

(this
can vary)
Streak
Luster


How Do You Determine a
Mineral’s Hardness?

 Friedrich

Mohs invented a
test to describe and
compare the hardness of
minerals
 Mohs Hardness Scale
Ranks ten minerals from
softest to hardest


How Does the Mohs Scale Work?
Gypsum

(2) will
scratch talc (1),
calcite (3) will
scratch gypsum
(2), fluorite (4) will
scratch calcite (3),
etc.


What Is a Streak Test?

 The

streak of a
mineral is the color of
its powder
 The streak color and
the mineral color are
often different
 To test: rub a mineral
against an unglazed
tile (streak plate)


What is the Luster of a
mineral?
 Luster

– used to describe

how a mineral reflects
light from its surface
 Minerals containing
metals are often shiny
 Earthy, waxy, and pearly


What does Density have to do
with Minerals?
 Each

mineral has a characteristic
Density
 Density – or mass per unit volume;
Density = mass/volume
 Displacement – the volume of the
displaced water equals the volume
of the the sample


What Kind of Shape does a
Mineral have?
 Minerals
 Cubic

have a crystal structure

 Hexagonal

 Tetragonal

 Orthorhombic
 Monoclinic
 Triclinic


What is Mineral Cleavage?

 Cleavage

–A
mineral’s ability to
split easily along a
flat surface
 The ability to break
apart depends on
the arrangement of
the atoms in the
mineral

Cubic Cleavage

Basal Cleavage


What is Mineral Fracture?
 Fracture

– How a mineral
looks when it breaks apart in

an irregular way


What Special Properties does a
Mineral have?
 Fluorescence

–minerals that
glow under ultraviolet light
 Magnetism - ex. Loadstone
 Chemical Reactivity- ex. Calcite
gives off carbon dioxide
 Electrical Properties – ex.
quartz


Section2:



How are Minerals Formed?

Two General Ways:
 Crystallization of melted materials
Minerals

from Magma

 Crystallization

in water

of materials dissolved

Minerals

from Hot water

Minerals

formed by

solutions

evaporation


What is Crystallization?
 Crystallization


the process by which
atoms are arranged to
form a material with a
crystal structure


How do Minerals form from
Magma?
 Minerals

form as magma
cools inside the crust, or as
lava hardens on the surface


What Effects Crystal Size?

 Rate

at which magma cools
Slower cooling forms
larger crystals
 The amount of gas the
magma contains
 The chemical composition of
the magma


How do Minerals Form from Hot
Water Solutions?

 Magma

beneath Earth’s
surface has heated the water
to a high temperature beneath
Earth’s surface causing
minerals to dissolve
 When this solution cools the

elements and compounds leave
the solution and crystallize as
minerals


What is a Solution?
 Solution

– A mixture in
which one substance
dissolves in another


What do Pure Metals often
form from Hot Water
Solutions?


Veins – A narrow channel or

slab of a

mineral that is much different from
the surrounding rock


How are Minerals Formed by
Evaporation?
 As

water turns to vapor it
leaves behind the mineral
 Example: A salt water
solution leaves behind large
crystals of salt