Download Mineral

Properties of
Minerals
Geologists use
characteristics to tell one
mineral from another
What is a mineral?
•S
•N
•I
•F
•C
olid
aturally Occuring
Inorganic
ixed Composition
Crystal Form
Groups of Minerals
• Minerals are grouped by the elements
they are made of.
Beryl (Emerald)
Calcite
Amethyst
Mineral Group
Characteristics
Contain
Silicates
oxygen & silica
The most
abundant group
of minerals
MICA
Examples
Quartz, mica
Quartz
Mineral Group
Characteristics
Make
Non-Silicates
Silver
up only
5% of the
Earth’s crust
Include some
of the most
important
minerals
Examples
iron, copper,
gold, silver,
diamonds,
rubies
Copper
Diamond
Gold
Ruby
Iron
Mineral Group
Carbonates
Characteristics
Carbon
Examples
&
Calcite (CaCO3)
oxygen and a
positive ion,
such as calcium
Calcite with Duftite inclusions
Mineral Group
Oxides
Characteristics
Metallic
ion
and oxygen
Examples
Hematite
(Fe2)O3
Mineral Group
Sulfides
Characteristics
Sulfur
and a
metallic ion
Examples
Galena (PbS)
Mineral Group
Sulfates
Barite on Calcite
BaSo4 / CaCO3
Characteristics
Metallic
Sulfur &
oxygen
ion,
Barite
BaSo4
Examples
Barite (BaSO4)
Mineral Group
Native
Elements
Characteristics
Single
elements
Examples
Gold (Au),
Diamond (C),
Silver (Ag)
How do minerals form?
• 1) Cooling of magma (hot, liquid rock and
minerals inside the earth (from the
mantle))
– Fast Cooling = No Crystals (mineraloids)
– Medium Cooling = small crystals
– Slow Cooling = large crystals
How do minerals form?
• 2) Elements dissolved in liquids (usually
water)
Mineral properties
•
•
•
•
•
•
•
Color
Luster
Habit (Shape)
Cleavage & Fracture
Streak
Hardness
Other
Luster:
How minerals reflect light
Metallic
Nonmetallic
Physical Properties of Minerals
(can be used to identify the mineral)
Luster
• Surface reflection
• metallic = shiny like
metal
• non-metallic = dull,
non-shiny surface
Pyrite has a metallic luster
Calcite has a non-metallic luster
Pyrite has metallic luster
Quartz has nonmetallic luster
Physical Properties of Minerals
(can be used to identify the mineral)
Hardness
• How easily a mineral scratches
materials
• Mohs Hardness Scale
• Scale from 1 (softest) to 10 (hardest)
• Test by seeing if the mineral can scratch
different objects (like human fingernail, copper,
penny, glass, steel file)
Gypsum is soft, it can be
scratched by a fingernail.
Calcite is soft, but a little harder
because it cannot be scratched by a
fingernail, but it can be scratched
by a penny.
Fluorite is harder. It can be
scratched by a nail, but not a
penny or fingernail.
Diamonds are the hardest mineral,
so it scratches every mineral.
Mineral Habit (Shape)
Shape a mineral
takes if grown
unimpeded
Physical Properties of Minerals
(can be used to identify the mineral)
Streak
• The color of the powdered
form of the mineral
• The color of the streak can be
different than the mineral
• Minerals must be softer than
the streak plate
Streak
• Red chalk on a chalk board makes
red marks. White chalk makes white
marks.
• Not all minerals work this way.
When some minerals are scratched
along a ceramic streak plate, it
creates a different color.
Gold
• When gold is run
across a streak
plate it makes a
yellowish-gold
color.
• That makes
sense.
Pyrite or “Fool’s Gold”
• When pyrite is run
across a streak plate,
it has a black or dark
green streak.
• Pyrite is not worth
much money, while
gold is worth a lot.
They look alike, so
miners call it fool’s
gold.
Hematite
• Hematite’s color is
grey, but its streak is
red.
• Hema means blood.
• The mineral was
named hematite
because it looked like
it was bleeding when
it was taken across a
streak plate.
Streak…can help identify quartz
http://www.childrensmuseum.org/geomysteries/cube/b3.html
Cleavage
•Not all minerals have cleavage.
•Some minerals split easily along a
flat surface.
•The number of lines that are
created when a mineral is split
will be the number of cleavage
lines.
Physical Properties of Minerals
(can be used to identify the mineral)
Cleavage & Fracture
– The way the mineral breaks
– Cleavage—minerals break
along smooth, flat surfaces
and every fragment has the
same general shape
– Fracture—minerals that break
at random with rough or
jagged edges
Fracture breaks irregularly in
all different shapes and sizes.
QUARTZ
Physical Properties of Minerals
(can be used to identify the mineral)
Color
• Can be misleading
• Can vary with the type of impurities
Color:
Not mineral specific
One mineral
property we will
use… is
COLOR
A mineral can be many different
colors. Below is Mica.
Many minerals can be the same color. Below are
gold colored minerals. Which one is gold?
The answer…
None of them were
real gold.
Physical Properties of Minerals
(can be used to identify the mineral)
Other Properties
– Specific gravity (*excellent clue to
mineral’s identity) Specific Gravity
– Attraction to magnets
– Bending of light
– Reaction with hydrochloric acid
– Smell & taste (Never taste anything in the
our school lab.)
Just like with people…
Outside color does not tell you
much about the important
characteristics.
What is a gem?



A Mineral OR Rock that has value
Rare !
Sometimes polishing or cutting will add
value