Minerals
Chapter 2
Matter
Matter includes anything that has mass
and takes up space (volume).
 It exists in 3 main states on Earth – solid,
liquid, and gas.
 Matter can be classified based on its
physical state, chemical composition &
structure.

Elements
Elements are the building blocks of
minerals.
 Elements cannot be broken down into a
simpler substance.
 95 naturally occurring elements
 Organized based on properties in the
Periodic Table of Elements

Periods on the Periodic Table
The periods are the rows on the periodic
table.
 Elements in the same period have the
same number of energy levels in their
electron cloud.

Groups on the Periodic Table
The groups are the columns on the
periodic table.
 Elements in the same group have similar
properties.
 The groups are also called families.

Atoms

Basic atomic structure
Compounds
Compounds form when two or more
elements combine making a substance
with different properties from the elements
that make it.
 For example: Salt or sodium chloride

Bonds – forming compounds

Atoms can form 3 types of bonds:
– involves a complete transfer of electrons;
occurs between metals & non-metals
 Covalent – involves the sharing of electrons;
occurs between two non-metals
 Metallic – occurs when two metals share
electrons
 Ionic
Why Do Atoms Form
Compounds?
Most atoms are not chemically stable by
themselves.
 They form chemical bonds with other
elements to become stable.
 Elements in Group 18 are chemically
stable by themselves.

Minerals must have the
following characteristics:
1. Naturally occurring – formed by a geologic
process
 2. Solid at Earth’s surface
 3. Crystalline structure – atoms are arranged in
an orderly & repetitive fashion
 4. Definite chemical composition – are
chemical compounds made of two or more
elements
 5. Inorganic… usually

Mineral Formation

Minerals generally form in one of 4
different ways:
 Crystallize
from magma
 Precipitation
 Changes in temperature & pressure
 Form from hydrothermal solutions
Crystallization from Magma
Elements combine to form minerals as
magma cools.
 Examples

 Feldspar
 Quartz
 Muscovite
(mica)
 Hornblende
Precipitation
Water holds a lot of dissolved substances.
 As it evaporates, it leaves behind many of
these substances.
 Changes in the temperature of the water
may also cause minerals to form.
 Examples

 Calcite
 Halite
(salt)
Pressure & Temperature
Changes in temperature and pressure can
cause minerals recrystallize or become
unstable.
 New minerals will form as a result.
 Examples

 Talc
 Muscovite
(mica)
Hydrothermal Solutions
Chemical reactions occur when hot water
(100-300 C) comes into contact with
minerals.
 New minerals form as a result of these
reactions.
 Examples

 Bornite
 Chalcopyrite
Mineral Groups
Minerals are placed into one of 6 groups
based on their composition.
 The 6 groups of minerals are

 Silicates
 Carbonates
 Oxides
 Sulfates
& Sulfides
 Halides
 Native
Elements
Silicates

Formed when silicon and
oxygen combine to form a
silicon-oxygen tetrahedron
 Bond



is very strong
Most common
Made of silicon and oxygen
Can form deep below
earth’s surface or at the
surface when other
minerals are exposed to
weathering

Example: garnet
Carbonates



2nd most common
Contain carbon,
oxygen, & at least
one metal
Example: calcite,
dolomite, limestone,
and marble
Oxides


Contain oxygen and
at least one other
element that is
usually a metal
Example: corundum
Sulfates & Sulfides


Contain sulfur
Examples:
 Gypsum
 Galena
Halides


Contain a halogen
from group 17 of the
periodic table and
another element
Examples
 Halite
 Fluorite
Native Elements


Only contain one
element
Examples
 Gold
 Silver
 copper
Properties of Minerals
Minerals are identified based on a variety of
physical and chemical properties.
 The seven properties used to identify
minerals are:

 Color
 Streak
 Luster
 Crystal
Form
 Hardness
 Cleavage
Fracture
Density
Color

Color is not a very reliable identifying
property for a lot of minerals.
 Small
amounts of the different elements can
give the same mineral different colors.

Some minerals, like sulfur, can be easily
identified based on color.
Streak

Streak is the color of
a mineral in its
powdered from
 Streaks
usually does
not vary from different
samples of the same
mineral

Use the white
porcelain plate and
the black plate to
check the streak of a
mineral.
Luster
Luster is used to describe how light is
reflected off the surface of a mineral
 Types of luster

– looks like metal
 Vitreous, glassy, pearly, silky, and earthy are
used to describe non-metallic lusters
 Metallic
Crystal Formation


Crystal formation is the
visible expression of a
mineral’s internal
arrangement of atoms
This can be difficult to
determine.
 Not
all crystals are allowed
enough room to grow and
do not immediately show a
well developed crystal
structure.
Hardness
Hardness is a measure of the resistance
of a mineral to being scratched
 Minerals tend to have a specific range of
hardness.
 The Mohs scale is used to measure
mineral hardness. 10 on the scales is the
hardest (diamond), 1 on the scale is the
softest (talc)

Mohs Scale of Hardness
Cleavage

Cleavage is the
tendency of a mineral
to cleave, or break,
along flat even
surfaces
Fracture


Minerals that do not
show cleavage when
broken.
Fracture is the
uneven breakage of a
mineral.
Density
Density can be used to determine the
purity or identity of minerals.
 Density is equal to the mass of the mineral
divided by the volume of the mineral.
 See pages 54-55 for a list of some
common minerals and their properties.

Distinctive Properties

Some minerals have
very distinctive
properties that are
unique to them.




Sulfur (smell)
Graphite (greasy feel)
Calcite (bubbles in
HCl)
Magnetite (is
magnetic)