baker 7th grade science mineral id how to identify a mineral by its properties

Baker 7th grade science

Mineral IDHow to identify a mineral by its properties


Today you will learn Which mineral

properties are most important in identification.

How mineral are identified by their properties.


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.


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.



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.



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


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.


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


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?


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.


Mineral Property #4Hardness A mineral’s hardness

is its resistance to being scratched.

A scale known as the Moh’s scale is often use


Mohs Scale


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.


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


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?


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


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

baker 7th grade science mineral id how to identify a mineral by its properties

Documents

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