Mineral Property Color

• 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 use to ID a mineral. Color can be confusing.

• Many minerals have different colors and some minerals' colors are identical to other minerals' colors.

Mineral PropertyStreak

• 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.

Mineral PropertiesColor & 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

Mineral Property - Luster

• 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 - 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 • Transparent – can you see through it?

Quick Check

• 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 Cleavage (or fracturing)

• 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 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.

Mineral Property Hardness

• 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 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.

Mineral Property 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

Brain Check

• 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 Lumpy Cats Die From HeatSome Llamas Climb Dirty Fat 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