2013_05Minerals - Minerals Unless specied otherwise, all...

Minerals
Unless specified otherwise, all photos, images, &
figures in this presentation are courtesy of W. W.
Norton.
• Know the definition of a mineral .
• Understand the basic physical properties of minerals and how to apply them.
• Be familiar with the parts of an atom .
• Understand the di ff erent types of bonding .
• Know the di ff erences between anions & cations , polymorphs & isotopes , and
atomic number & atomic weight .
• Learn about the silica tetrahedron and how it linkages in silicate minerals impart
some of their physical properties.
Some key points to keep in mind...

•
A mineral is defined as a substance that meets the following 5 criteria:
• solid
• naturally occurring (nothing synthetic)
• mostly inorganic (not coal-- mineral resource )
• a definite chemical composition (minor substitutions)
• a definite crystalline structure (not disorderly- glass )
• Rocks are an aggregate of minerals.
Minerals
• a definite chemical composition (minor substitutions)
Minerals

• a definite crystalline structure
(not disorderly- glass )
• Ordered atoms in crystals form a lattice
(patterns that repeat in 3 dimensions).
• This internal pattern controls mineral properties:
• Crystal shape
• Symmetry
• Cleavage
Minerals
glass
• Characteristics determined by your 5
senses
• Used to ID minerals
• Properties depend upon…
• Chemical composition.
• Crystal structure.
• Some are diagnostic.
• Example: Pyrite (FeS
2
)
• Cubic crystals, high specific gravity, striated crystal faces,
black streak, metallic luster, dull brassy color, sulfur smell
when crushed, erroneously mistaken for gold (fool’s gold).
• Minerals have a unique set of physical
properties
(just like individuals in this classroom).
Minerals
Physical Properties
Pyrite
• Color
• Luster
• Streak
• Hardness
• Specific Gravity
• Crystal Form
• Fracture
• Cleavage
• Striations
• Tenacity
• Reaction to HCl
acid
• Magnetism
• Taste
• Odor
• Feel
Common Physical Properties

• The appearance of a fresh mineral surface in
reflected light is the luster .
Minerals
Physical Properties
Metallic Luster Non-Metallic Luster
Metallic freshly broken metal
Sub-Metallic dull metal
Don't confuse with dark glassy
minerals!
Vitreous glassy
Resinous resin-like, waxy
Pearly pearl-like sheen
Adamantine brilliant luster like
that of a diamond
Dull or Earthy luster of clay or
dirt
Satin spar Gypsum – Satiny luster
Quartz – Vitreous luster
• The color of a mineral is determined by
examining a fresh surface in reflected
light.
• Color is typically undiagnostic because
slight impurities can dramatically change
the color of a mineral (see quartz).
• Color may be helpful for minerals with a
metallic luster and dark-colored minerals
with a non-metallic luster.