Baker 7th grade science
Mineral IDHow to identify a mineral by its properties
Baker 7th grade science
Today you will learn Which mineral
properties are most important in identification.
How mineral are identified by their properties.
Baker 7th grade science
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.
Baker 7th grade science
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.
Baker 7th grade science
Baker 7th grade science
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.
Baker 7th grade science
Baker 7th grade science
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
Baker 7th grade science
Mineral Property # 2Luster A mineral’s luster is
the way in which light reflects from the surface.
The two major types of luster are metallic & nonmetallic.
Baker 7th grade science
Baker 7th grade science
Mineral Property # 2Luster
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
Baker 7th grade science
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?
Baker 7th grade science
Mineral Property # 3How 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.
Baker 7th grade science
Baker 7th grade science
Mineral Property # 3How 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.
Baker 7th grade science
Baker 7th grade science
Mineral Property #4Hardness A mineral’s hardness
is its resistance to being scratched.
A scale known as the Moh’s scale is often use
Baker 7th grade science
Baker 7th grade science
Mohs Scale
Baker 7th grade science
Mineral Property #5Density
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.
Baker 7th grade science
Baker 7th grade science
Mineral Property #5Density
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
Baker 7th grade science
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?
Baker 7th grade science
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
Baker 7th grade science
SLCDFHSome Llamas Climb Down Funny Hills
SStreak Powdered Color
LLuster How shiny
CCleavage Breaks in sheets or blocks
DDensity How much mass in a given volume
FFracture Just crumbles & breaks
HHardness Can be scratched by