Minerals
A mineral is a naturally
occuring, inorganic,
crystalline solid with a specific
chemical composition.
NATURAL
INORGANIC
Minerals are created by
the Earth itself…not
from human influence.
Minerals are not made by
living things or are
composed of living things.
CRYSTALLINE
CHEMICAL
COMPOSITION
The arrangement of atoms
within a mineral creates a
crystalline structure. Each
mineral has its own unique
structure.
Minerals are composed
of one element or many
elements in the form of
a compound.
Chemical Composition
of Minerals
Some minerals are
composed of a
single element.
Ex: Sulfur = S
Some minerals are
composed of a
combination of
elements known as
a compound.
RT = Pg. 16
Ex: Fluorite = CaF2
(combination of
calcium and
fluorine)
Crystalline Structure
of Minerals
The atoms with a mineral are arranged and bonded in a
specific way creating the crystalline structure of the
mineral.
The crystalline structure of a mineral helps to determine
that mineral’s physical and chemical properties – such as
hardness and cleavage.
The majority of the Earth’s crust
(by mass and volume) is made
up of the elements oxygen and
silicon. The “silicon-oxygen
tetrahedron” is the basic
building block of many minerals.
The arrangement of silicon-oxygen tetrahedrons
determines the crystalline structure of minerals.
Rock vs.
Mineral
A rock is a naturally formed solid that is
part of the Earth.
All minerals are rocks, but not all rocks
are minerals.
Most rocks are composed of one or more
minerals. Some rocks are composed of
glassy or organic materials
COAL
OBSIDIAN
Coal is composed of the organic
remains of ancient plant and
animal matter (organic).
Obsidian is volcanic glass that is formed by
heated rock being cooled very quickly. Glass has
a noncrystalline atomic structure.
Minerals are inorganic.
Minerals have a crystalline structure.
Mineral Properties
and Identification
The best method for
mineral
identification is
through the use of Xray diffraction.
A beam of X-rays
passing through a
mineral sample will
diffract leaving a
unique “x-ray
pattern” on
photographic film.
Each mineral has its
own unique
diffraction pattern.
Minerals have a unique set of physical and chemical
properties that reflect its internal arrangement of
atoms. When in the field, scientist will use other
methods to identify minerals.
Mineral Properties
and Identification
SULFUR
Sulfur is well known for
its yellow color.
Color
QUARTZ
All three samples are of
the same mineral. In
this case color would not
be useful tool in mineral
identification.
The color of a mineral can be used for identification in some
cases. Many times minerals will change due to impurities found
within the rock or mineral.
Color is NOT a reliable mineral property used in identification
Mineral Properties
and Identification
Streak
The residue of a mineral
left on a scratch plate is
known as streak.
The streak color does not
always match the color of
the mineral.
HEMATITE
Hematite is a silver colored mineral.
When scratched on a porcelain
plate, its streak is reddish-brown.
The streak of a mineral is
more consistent than the
color of a mineral and,
therefore, is a more
reliable test for mineral
identification.
Mineral Properties
and Identification
PYRITE
Pyrite has a metallic luster and
shines like a metallic surface in the
light.
Luster
OLIVINE
Olivine does not shine like a metallic
surface in the light. It has a
nonmetallic luster.
The shine from an unweathered mineral in light is known as luster.
Minerals may have metallic or nonmetallic lusters.
A mineral with a metallic luster shines like a metallic surface (Ex: clean steel
pot).
Most minerals have a nonmetallic luster.
Mineral Properties
and Identification
Hardness
Gypsum has a hardness of 2 and
calcite has a harness of 3. A
fingernail has a hardness of 2.5.
A fingernail can “scratch”
gypsum and “be scratched” by
calcite.
The resistance to being scratched is known as a mineral’s
hardness.
Moh’s Hardness Scale is a tool used by scientists to determine the
hardness of a mineral. Scientists can determine whether an
unknown mineral can “scratch” or be “scratched” by known
common materials. This will help a scientist determine the
hardness of an unknown mineral.
Mineral Properties
and Identification
Cleavage
The tendency of a mineral to
break along a zone of
weakness is known as
cleavage.
MUSCOVITE MICA
CLEAVAGE:
Zones of
weakness
Zones of weakness found
within a mineral relate to
the crystalline structure of
the mineral.
Sometimes zones of weakness
can be seen as smooth sides
with a luster.
GALENA
FRACTURE:
Uneven brake
Minerals that lack zones of
weakness will break or
“cleave” along uneven
surfaces. This is known as
fracture.
Mineral Properties
and Identification
Specific
Gravity
Crystal
Shape
Reaction with
HCl acid
Other Tools for
Mineral Identification
Specific gravity is the
density of a mineral
compared to that of
water.
The geometric
shape a mineral
takes is known as
crystal shape.
Certain minerals
will react in the
presence of
hydrochloric acid.