aim: how can we describe a mineral?
DESCRIPTION
Turn and Talk Take one minute with your partner next to you and discuss what you think a mineral is.TRANSCRIPT
Aim: How can we describe a mineral?
Turn and Talk
• Take one minute with your partner next to you and discuss what you think a mineral is.
So what is a mineral?A mineral must meet the following
five characteristics. All rocks are made of minerals
What are the 5 characteristics of all minerals?
1. A mineral occurs naturally.
2. A mineral is solid.
3. A mineral has a definite chemical composition.
3. A mineral has a definite chemical composition.
• Find the ESRT page that deals with minerals.
• What is the composition of halite?
• Quartz
TTYP
• What are the two most common elements in all minerals?
Average Crustal Composition
• What two elements are the most abundant by mass in the crust?
• Oxygen• Silicon
4. A mineral’s atoms are arranged in an orderly pattern.
5. A mineral is inorganic(was never alive)
Mineral or Not?
Water
Gold
Pearls
Mineral or Not?
Diamond Coal
Silver
These minerals make up most of the rocks found in the Earth’s crust.
Of the almost 4000 known minerals, only about 30 are common.
The most common are
quartz
feldspar
micacalcite
Minerals are arranged into groups…
• According to their chemical and physical properties.
Mineral Groups
•Silicates•The most common (silicon & oxygen)
•Other groups include:•Carbonates
•Sulfides
•Oxides
•Halides
•Hydroxides
•Sulfates
The molecular structure is called a silica tetrahedron
The importance of MineralsWithout a proper intake of zinc the immune system can become vulnerable and normal human growth can be delayed. Zinc also plays a key role in our ability to heal wounds
Turn and Talk
• With your partner look at p. 16 of your reference table and find some common uses for minerals.
Identification of Minerals
To be able to identify these and other minerals, we need to look at the properties used to separate and
distinguish these minerals.
Remember!:You cannot identify a mineral only
using one property.These properties need to be
considered together to correctly identify a mineral.
1. Color
• What color the mineral is.• Color is the most easily observed
mineral property and the least useful!
ColorMany minerals have a similar
color.
ColorsMany minerals can turn colors due
to impurities, or they can change colors in various circumstances.
Color
For example, pure quartz is colorless or white, impurities can make the mineral rose, purple or
pink!
Some exceptions to the color rule would be cinnabar, which is
always red, and malachite, which is green.
2. Streak
Streak of a mineral is the color of its powder when rubbed on an
unglazed white tile.Test: rub the mineral on a tile.
Streak
The streak is often not the same color as the mineral.
A minerals color may vary, but the streak rarely will!
3. Luster
Luster refers to the way a mineral shines in reflected light.
Notice the difference between these two minerals?
3. Luster
The mineral on the left has a metallic luster, the one on the
right, a nonmetallic luster.
Metallic or Non-metallic?
• Metallic• Galena
Metallic or Non-metallic?
• Non-metallic• Quartz
Metallic or Non-metallic?
• Metallic• Pyrite aka fool’s gold
4. Hardness
The hardness of a mineral is its resistance to being scratched.
Diamond is the hardest of all minerals, and talc is the softest.
The harder one will always scratch the softer one
Common hardness tests
• Unpolished finger nail = 2.5• Steel = 4.5• Glass = 5.5
4. Hardness
Friedrich Mohs devised a hardness scale.
In this scale, ten well known minerals are given numbers from one to ten.Lets take a look at the ten minerals used and some of the simple tests.
Talc (left) is the softest and has a hardness of 1. A soft pencil lead will scratch talc.
Gypsum is a bit harder and has a hardness of 2. A fingernail scratches gypsum.
Calcite (left) has a hardness of 3 and a copper penny just scratches it.
Fluorite has a hardness of 4 and it can be scratched by an iron or brass nail.
Apatite (left) has a hardness of 5 and can be scratched by a steel knife blade.
Feldspar has a hardness of 6 and it will scratch a window glass.
Quartz (left), with a hardness of 7, is the hardest of the common minerals. It easily
scratches hard glass and steel.Topaz has a hardness of 8 and will scratch
quartz.
Corundum (left) has a hardness of 9. Corundum will scratch topaz.
Diamond with its hardness of 10 can easily scratch the rest of the minerals.
Hardness finder!
• Find a mineral that is softer than calcite. • Find a mineral that would scratch quartz.• Find a mineral that fluorite would scratch.
On your own
• Create two questions using the hardness scale.
5. Cleavage
The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces.
Cleavage can even be observed on tiny mineral grains making it a very useful
property!
5. Cleavage
Mica is probably the best example as it splits into thin sheets. It is said to
have one perfect cleavage.
Cleavage
Feldspar splits readily in two directions, always at or near right angles.
5. Cleavage
Not all minerals show cleavage.Those that don’t break along cleavage
surfaces are said to have fracture.
Cleavage or Fracture?
• Cleavage• Halite
Cleavage or Fracture?
• Fracture• Quartz
Cleavage or Fracture?
• Cleavage• Biotite Mica
Cleavage or Fracture?
• Fracture• Olivine
6. Reaction to Acid
Calcite is calcium carbonate, CaCO3. If a drop of weak hydrochloric acid is
placed on calcite, the acid bubbles as carbon dioxide is released.
7. Other special properties
Malleable
Magnetic
Radioactive
Flourescence
Taste
Turn and talk: Looking at the samples below and what you’ve learned about minerals today what properties do you think you would use to identify them?