1. How to identify a mineral by its properties
Mineral ID
How to identify a mineral by its properties
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2. Today you will learn
Which mineral properties are most important in identification.
How mineral are identified by their properties.
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3. A mineral’s appearance helps identify it.
In order to identify a mineral, you need to observe it properties – characteristics that help identify it.
There are 5 main properties that we use to identify. There are many minor properties that can also help id a mineral.
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4. Mineral Property #1 Color & Streak
Color is the first thing someone notices when they view a mineral.
Color is also one of the big reasons that attract people to minerals.
Generally speaking, color is not a good property to be used in the identification of minerals. It is usually the first property to confuse a novice collector into making an incorrect identification.
Many minerals have different colors and some minerals' colors are identical to other minerals' colors.
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6. Mineral Property #1 Color & Streak
Streak is closely related to color, but is a different property because the color of the mineral may be different than the color of the streak.
Streak is actually the color of the powder of a mineral. It is called streak because the proper way to test for streak is to rub a mineral across a tile of white unglazed porcelain and to examine the color of the "streak" left behind.
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8. Mineral Property #1 Color & Streak
Pyrite (known as "Fool's Gold") is always brassy yellow when found in crystals, even broken crystals, of any size; but when powdered, produces a black streak.
Gold's streak, by the way, is yellow!
Hematite's streak is blood-red
Galena's streak is lead gray
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9. Mineral Property # 2 Luster
A mineral’s luster is the way in which light reflects from the surface.
The two major types of luster are metallic & nonmetallic.
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11. Mineral Property # 2 Luster
Some other ways to describe luster are
Dull - just a non-reflective surface of any kind
Earthy - the look of dirt or dried mud
Fibrous - the look of fibers
Greasy - the look of grease
Gumdrop - the look a sucked on hard candy
Metallic - the look of metals
Pearly - the look of a pearl
Pitchy - the look of tar
Resinous - the look of resins such as dried glue or chewing gum
Silky - the look of silk, similar to fibrous but more compact
Submetallic - a poor metallic luster, opaque but reflecting little light
Vitreous - the most common luster, it simply means the look of glass
Waxy - the look of wax
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12. Quick Check Get out your whiteboard and quickly answer the following:
What is the first thing someone notices about a mineral?
What do we call the color of the powdered mineral?
Which is more reliable: streak or color?
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13. Mineral Property # 3 How a mineral breaks
When a mineral breaks it does so either by fracturing or by cleaving.
Cleavage is the tendency of a mineral to break along flat surfaces.
Crystal cleavage is a smooth break producing what appears to be a flat crystal face.
Fracture is the tendency of a mineral to break into irregular pieces.
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15. Mineral Property # 3 How a mineral breaks
When a mineral breaks it does so either by fracturing or by cleaving.
Cleavage is the tendency of a mineral to break along flat surfaces.
Crystal cleavage is a smooth break producing what appears to be a flat crystal face.
Fracture is the tendency of a mineral to break into irregular pieces.
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17. Mineral Property #4 Hardness
A mineral’s hardness is its resistance to being scratched.
A scale known as the Moh’s scale is often use
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19. Mohs Scale
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20. Mineral Property #5 Density
Each mineral has a specific density.
Density is the mass of a given space or in scientific terms the mass per unit of volume.
For example, if you have two minerals of the same size one might be heavier than the other. The galena will be three times heavier than the same size of quartz.
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22. Mineral Property #5 Density
Geologists measure density by the following:
First they use a balance to determine the mass of a sample.
Second, they place the mineral in water to see how much water it displaces.
The volume of displace water = the volume of the sample
Third they use the following formula:
Density = Mass/Volume
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23. Brain Check Get out your whiteboard and quickly answer the following:
If you break a mineral and it breaks into cubes, is it fracture or cleavage? Why?
If you break a mineral with a hammer and it falls apart into a million different pieces, is it fracture or cleavage? Why?
Name three things you can scratch talc with.
What is the formula for density?
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24. Some minerals have specific properties
Fluorescence: some minerals glow when exposed to ultraviolet light
Magnetic: Some minerals are attracted to magnets
Acid: Some minerals react with acid by bubbling
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25. SLCDFH Some Llamas Climb Down Funny Hills
Streak
Powdered Color
Luster
How shiny
Cleavage
Breaks in sheets or blocks
Density
How much mass in a given volume
Fracture
Just crumbles & breaks
Hardness
Can be scratched by
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