Mineral - A naturally occurring, inorganic,
homogeneous solid with a definite chemical composition
and an ordered atomic arrangement.
naturally occurring - materials synthesized in laboratory do not count,
must be formed by natural processes in wild
inorganic - not formed by organic chemistry (e.g., sugars, etc.)
homogeneous solid - single substance in solid phase which cannot
be physically separated into simpler compounds
definite chemical composition - composition can be represented as
chemical formula (e.g., NaCl), although variation in exact composition
is possible (e.g., (Mg, Fe)2SiO4 ) [range in color, hardness, specific
gravity]
ordered atomic arrangement – repeating structure at the atomic level,
which expresses as symmetry in large specimens, i.e., crystalline
structure.
http://www.uoregon.edu/~jrice/geol311
Mineral Properties
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak Color
Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Crystal symmetry is controlled by the
atomic structure of mineral
Mineral Properties
• Crystal Form
• Cleavage/Fracture
Color
• Streak Color
• Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Characteristic for some minerals, useless for most
Quartz
Jasper
Citrine
Rose Quartz
Quartz
SiO2
Amethyst
Hardness = 7
Carnelian
Onyx
Smokey
Quartz
Mineral Properties
• Crystal Form
• Cleavage/Fracture
• Color
Streak Color
• Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Streak Color - Color of powdered mineral, which
may or may not be the color of the crystal
Streak:
Color of powdered mineral on porcelain plate
Hardness ~ 6.5
Good for metallic opaque minerals,
Not good for silicates, transluscent/transparent minerals, and minerals harder
than the streak plate (color of streak plate)
Pyrite
Hematite
Mineral Properties
•
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak
Luster
• Hardness
• Tenacity
Specific Gravity
• Acid Test
• Magnetism
Specific Gravity - density of the material (g/cm3)
Specific Gravity
Related to both the atomic weight of the contained
elements, and how tightly the atoms are packed
Orthorhombic Carbonates
All minerals have same structure, only cation differs
Mineral
Formula
Cation
g/cm3
Aragonite
CaCO3
20
2.95
Strontianite
SrCO3
38
3.76
Witherite
BaCO3
56
4.29
Cerrusite
PbCO3
82
6.55
Mineral Properties
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak Color
Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Luster - quality of light reflected from mineral surface
Luster - quality of light reflected from mineral surface
pyrite
metallic
gold
silver
Luster quality of light reflected from mineral surface
non-metallic
Some minerals may be listed in
both metallic and non-metallic, or
in the incorrect table, i.e., limonite
pearly
vitreous (glassy)
resinous
Mineral Properties
•
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak Color
Luster
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Hardness - resistance of mineral
to scratching or abrasion
Hardness: resistance to scratching
Compare with other objects or other mineral of known hardness. Some
minerals can have a varying hardness due to impurities
Glass Plate (H = 5.5), very good test.
Muscovite
Hardness < 2
Can scratch with fingernail (H=2.5)
Fig. 02.14
Fluorite
Hardness =4
Fig. 02.15c
Can scratch copper penny (H=3.5),
but not glass plate (H=5.5)
Quartz
Hardness =7
Fig. 02.15a
Scratches glass plate (H=5.5).
Hardest of common minerals
Mineral Properties
•
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak
Luster
• Hardness
• Tenacity
• Specific Gravity
Acid Test
• Magnetism
Reaction to dilute acid; especially useful
in identifying carbonate minerals
Minerals like calcite react with weak acid, dissolving the
mineral and producing lots of bubbles (effervescence)
Calcite: CaCO3
HCl + CaCO3 > H2O + Cl- + Ca+ + CO2
Dolomite: CaMg(CO3)2
Mineral Properties
•
•
•
•
•
Crystal Form
Cleavage/Fracture
Color
Streak
Luster
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Some minerals strongly attract magnets. Characteristic
of magnetite and some other iron minerals
Mineral Properties
• Crystal Form
Cleavage/Fracture
• Color
• Streak Color
• Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Fracture - any breakage that is not cleavage
Page 82
Cleavage:
Breaks along planes of weakness
See the way light reflects back at you
(I cannot see this for you). Rotate the
mineral to “find” reflective surfaces.
When you find a cleavage plane,
rotate
Page 82
Page 82
Page 82
Page 82
conchoidal
fracture
Characteristic of quartz,
chert and flint
conchoidal
fracture
Fig. 02.23
Mineral Properties
• Crystal Form
Cleavage/Fracture
• Color
• Streak Color
• Luster
•
•
•
•
•
Hardness
Tenacity
Specific Gravity
Acid Test
Magnetism
Cleavage - tendency to split along planes of weakness
corresponding to weaker chemical links in internal
structure of crystal
One Direction
of Cleavage
Page 83
Page 83
Page 83
Page 83
Page 83
Page 83
Page 83
Page 90
Page 91
Page 92
Alphabetical
Page 90