Download Ch. 5 Lecture

Physical Geology
Chapter 5
Big Definition!
• Mineral – a natural, usually inorganic solid
that shows
– Characteristic chemical composition
– Orderly internal structure
– Recognizable physical properties
Is it organic?
Does it occur naturally?
Is it a crystalline solid?
Does it have a consistent
chemical composition?
Coal
Brass
Obsidian
Basalt
Fluorite
No
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
Yes
Yes
No
Yes
Kinds of Minerals
• Silicates – has some combination of
silicon (Si) and oxygen (O) and comprise
96% of the earth’s crust
• Non-silicates – no SiO compounds; 4% of
the earth’s crust
Silicate Minerals
• Quartz – only Si and O
• Feldspar – most common silicate
• Ferromagnesians – iron and magnesium
bearing compounds
– olivine
– Pyroxene
– Amphibole
– biotite
Non-Silicate Minerals
And Native Elements
• All minerals in Earth’s crust have a
crystalline structure of some kind.
• That is its “regular orderly structure”
What is a crystal?
• A solid whose atoms, ions, or molecules
are arranged in a regular, repeating
pattern
• X-rays are used to study crystals
• X-rays pass through a crystal and strike a
photographic plate producing an image of
the atom/molecule arrangement
Diamond
Silicate building block – the
silicon/oxygen tetrahedron
Silicate Mineral
Arrangements
•
•
•
•
•
Isolated do not link to other O or Si
Rings link by sharing O
Single chains share O (open rings)
Double chains are bonded single chains
Sheets share 3 O with others; 4th with Al or
Mg, which holds sheets
• Frameworks bond each tetrahedron to 4
others; and on and on…………..
Non-silicate arrangement
• Vast variety of crystalline structures
• May have tetrahedra similar to silicates but
with different elements at center
• Minerals with same ion at center share
properties, thus creating subgroups
How do we identify minerals?
• By physical properties such as
– Color
– Streak
– Luster
– Cleavage and fracture
– Hardness
– Crystal shape
– density
• Or by special properties such as
– Fluorescence
– Phosphorescence
– Chatoyancy
– Asterism
– Magnetism
– Radioactivity
– Double refraction
Color
• Many typical colors, but additions of
elements can cause changes; e.g.,
• quartz
vs.
Amethyst
Click here for more information
Streak
Click here for more information
Luster
• Click here for more information
Cleavage and fracture
• Click here for more information
Hardness
• Click here for more information
Crystal shape
• Click here for more information
Specific gravity
• Click here for more information
Special properties
• Click here for more information