A mineral is a naturally occuring, inorganic, crystalline solid with a specific chemical composition.
NATURAL
Minerals are created by the Earth itself…not from human
influence.
INORGANIC
Minerals are not made by living things or are composed of living
things.
CRYSTALLINE
The arrangement of atoms within a mineral creates a crystalline structure. Each mineral has its own unique
structure.
CHEMICAL COMPOSITION
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.
Ex: Fluorite = CaF2
(combination of calcium and fluorine)RT = Pg. 16
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. MineralA 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
Coal is composed of the organic remains of ancient plant and
animal matter (organic).
Minerals are inorganic.
OBSIDIAN
Obsidian is volcanic glass that is formed by heated rock being cooled very quickly. Glass has a
noncrystalline atomic structure.
Minerals have a crystalline structure.
Mineral Properties and Identification The best method for
mineral identification is through the use of X-ray
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 Color
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
SULFURSulfur is well known for
its yellow color.
QUARTZAll three samples are of
the same mineral. In this case color would not be useful tool in mineral
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.
The streak of a mineral is more consistent than the
color of a mineral and, therefore, is a more reliable
test for mineral identification.
HEMATITEHematite is a silver colored mineral.
When scratched on a porcelain plate, its streak is reddish-brown.
Mineral Properties and Identification 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.
PYRITEPyrite has a metallic luster and
shines like a metallic surface in the light.
OLIVINEOlivine does not shine like a metallic
surface in the light. It has a nonmetallic luster.
Mineral Properties and Identification Hardness
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.
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.
Mineral Properties and Identification Cleavage
The tendency of a mineral to break along a zone of weakness
is known as 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.
Minerals that lack zones of weakness will break or “cleave” along uneven surfaces. This is
known as fracture.
MUSCOVITE MICA
GALENA
CLEAVAGE:Zones of weakness
FRACTURE:Uneven brake
Mineral Properties and Identification
Other Tools for Mineral Identification
Specific Gravity
Specific gravity is the density of a
mineral compared to that of water.
Crystal Shape
The geometric shape a mineral
takes is known as crystal shape.
Reaction with HCl acid
Certain minerals will react in the presence of hydrochloric acid.