Mineral AppearanceMineral Appearance

Individual minerals have unique Individual minerals have unique propertiesproperties that distinguish them.that distinguish them.

ColorColor and and appearanceappearance are two obvious are two obvious clues that can be used to identify minerals.clues that can be used to identify minerals.

These clues alone are not enough to These clues alone are not enough to distinguish most minerals. Pyrite and distinguish most minerals. Pyrite and goldgold are the same color and can appear similar. are the same color and can appear similar. You need to look at the other You need to look at the other propertiesproperties to to tell them apart.tell them apart.

HardnessHardness

A measure of how easily a mineral can be scratched is A measure of how easily a mineral can be scratched is called its called its hardnesshardness..

The mineral The mineral talctalc is so soft that you can scratch it with your is so soft that you can scratch it with your fingernailfingernail. . DiamondsDiamonds are the hardest mineral. are the hardest mineral.

In 1824, Friedrich Mohs developed a list of common In 1824, Friedrich Mohs developed a list of common minerals to compare their minerals to compare their hardnesshardness. This list is called the . This list is called the Mohs scale of hardnessMohs scale of hardness..

The scale lists the hardness of The scale lists the hardness of tenten minerals. Talc is the minerals. Talc is the softestsoftest and has a hardness value of and has a hardness value of oneone. Diamond is the . Diamond is the hardesthardest and has a hardness value of and has a hardness value of tenten. .

Moh’s Hardness ScaleMoh’s Hardness Scale

LusterLuster

LusterLuster is the way a mineral reflects light. is the way a mineral reflects light. Luster can be Luster can be metallicmetallic or or nonmetallicnonmetallic.. Minerals with a metallic luster shine like Minerals with a metallic luster shine like

metalmetal, like gold or , like gold or graphitegraphite.. Minerals with a nonmetallic luster can be Minerals with a nonmetallic luster can be

described as dull, described as dull, pearlypearly, silky, or , silky, or glassyglassy, , like quartz and like quartz and halitehalite..

LusterLuster

Specific GravitySpecific Gravity

The The specific gravityspecific gravity of a mineral is the ratio of its of a mineral is the ratio of its weightweight compared with the weight of an equal compared with the weight of an equal volume of volume of waterwater..

Specific gravity is expressed as a Specific gravity is expressed as a numbernumber.. The specific gravity of gold is The specific gravity of gold is 1919, which means , which means

that gold is 19 times that gold is 19 times heavierheavier than water. than water. The specific gravity of pyrite is The specific gravity of pyrite is 55, which means , which means

that pyrite is 5 times heavier than that pyrite is 5 times heavier than waterwater, and that , and that pyrite feels much pyrite feels much lighterlighter than an equal-sized than an equal-sized sample of gold.sample of gold.

Specific GravitySpecific Gravity

StreakStreak

When a mineral is rubbed against a piece of When a mineral is rubbed against a piece of unglazed unglazed porcelainporcelain tile, a streak of tile, a streak of powdered mineral is left behind. powdered mineral is left behind. Streak Streak is is the color of a mineral in its powered form.the color of a mineral in its powered form.

The streak test only works for minerals that The streak test only works for minerals that are are softersofter than the streak plate. than the streak plate.

Graphite Graphite is used in pencil lead because it is is used in pencil lead because it is soft enough to leave a streak on soft enough to leave a streak on paperpaper..

StreakStreak

Cleavage and FractureCleavage and Fracture

The way a mineral The way a mineral breaksbreaks is another clue to is another clue to its identityits identity

Minerals that break along smooth, flat Minerals that break along smooth, flat surfaces have surfaces have cleavage.cleavage.

Mica Mica is a mineral that breaks along smooth, is a mineral that breaks along smooth, flat planes.flat planes.

Minerals that break with uneven, rough, or Minerals that break with uneven, rough, or jagged surfaces have jagged surfaces have fracture.fracture.

Quartz Quartz is a mineral with fracture.is a mineral with fracture.

CleavageCleavage

FractureFracture

Other PropertiesOther Properties

Some minerals have unique Some minerals have unique properties.properties. MagnetiteMagnetite is attracted to magnets. is attracted to magnets. Light forms two separate rays when is Light forms two separate rays when is

passes through passes through calcitecalcite, causing you to see a , causing you to see a double double imageimage..

Calcite alsoCalcite also fizzes fizzes when hydrochloric when hydrochloric acidacid is is put on it.put on it.

Unique PropertiesUnique Properties

Taste like salt (Halite)Taste like salt (Halite)

Smells like eggs (sulfur)Smells like eggs (sulfur)

GemsGems

GemsGems, or gemstones, are highly prized, or gemstones, are highly prized minerals minerals because they are because they are rarerare and and beautiful.beautiful.

Most gems are special varieties of a particular Most gems are special varieties of a particular mineralmineral. They are clearer, . They are clearer, brighterbrighter, or more , or more colorfulcolorful than common samples of that mineral. than common samples of that mineral.

In addition to their beauty, some gems serve In addition to their beauty, some gems serve useful useful purposespurposes. Because . Because diamondsdiamonds are so hard, are so hard, they are useful as cutting tools. they are useful as cutting tools. RubiesRubies can be can be used to produce types of laser light and used to produce types of laser light and quartzquartz crystals are used in electronic and timepieces.crystals are used in electronic and timepieces.

OresOres

A mineral or a rock is an A mineral or a rock is an oreore if it contains a if it contains a useful useful substance that can be mined at a profit.substance that can be mined at a profit.

Iron is obtained from its ore Iron is obtained from its ore hematite.hematite. Aluminum is refined from the ore Aluminum is refined from the ore bauxitebauxite. . Smelting Smelting

is the process by which aluminum oxide powder is is the process by which aluminum oxide powder is converted to aluminum.converted to aluminum.

Aluminum is made into useful products like Aluminum is made into useful products like bicyclesbicycles, soft-drink cans, and parts for cars and , soft-drink cans, and parts for cars and airplanes.airplanes.

Vein MineralsVein Minerals

Metallic elements can dissolve in Metallic elements can dissolve in fluidsfluids. . These fluids can travel through weaknesses These fluids can travel through weaknesses in in rocksrocks and form and form mineral deposits.mineral deposits.

Mineral deposits left behind that fill in the Mineral deposits left behind that fill in the open spaces created by the open spaces created by the weaknessesweaknesses in in rock are called rock are called veinvein mineral deposits. mineral deposits.