Download Minerals

Minerals
A mineral is
a.
NATURAL
INORGANI
C
CRYSTALLI
NE
CHEMICAL
COMPOSITI
ON
Chemical Composition
of Minerals
Ex: Sulfur =
S
RT = Pg. 16
Ex: Fluorite
= CaF2
(combinatio
n 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.
Rock vs.
Mineral
A rock is a
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
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
Mineral Properties
and Identification
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.
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.
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
MUSCOVITE MICA
CLEAVAGE:
Zones of
weakness
GALENA
FRACTURE:
Uneven brake
Cleavage
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.
Mineral Properties
and Identification
Specific
Gravity
Crystal
Shape
Reaction with
HCl acid
Other Tools for
Mineral Identification