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Unit 3: Earth MaterialsLesson 1: Identifying Minerals(Heath Earth Science pg. 46-61)

Todays ObjectivesDifferentiate between rocks and minerals, including:Use physical and chemical properties to identify and classify selected rocks and mineralsRocks and MineralsMineral: a naturally occurring inorganic solid substance with a definite chemical composition and structure (pg. 34)Rock: a group of minerals bound together (pg. 63)So in other words,

There are nearly 5000 known mineral species on earth

Rocks are made of minerals

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Identifying Minerals Using Their Physical PropertiesThis concept of will be Broken down into 2 or 3 LessonsToday we will practice using 6 different properties associated with mineral identificationLab Activity next day?

5Identifying MineralsIdentifying minerals are determined by composition and crystal structure.With this being said you dont need to know the chemical composition or crystal structure to identify what mineral you have.The first objective is to first determine the set of properties that are characteristic of the mineral

6The properties most often used to identify minerals are:Crystal form growth habitCleavageLusterColorHardnessSpecific GravityMagnetismStreakEffervescence (HCl rxn)Fluorescence

*We will look at the properties listed in red7LusterThe quality and intensity of the light reflected from the mineralTwo most important lusters are:MetallicNon-Metallic:Vitreous (glass)Resinous (resin)PearlyGreasySilkyEarthyAdamantineWaxy

8Luster

SilkyVitreousGreasyPearlyResinousWaxyMetallicEarthy/DullAdamantine

10Color and StreakColor identification can be confusing and misleading therefore it is important to streak a specimen on a nonglazed porcelain plate, called a streak-plateThis provides a reliable color effect because there are no impurities that can skew the streak

11HardnessHardness is the relative resistance of a mineral to being scratchedThis is a distinctive property of mineralsGoverned by the crystal structure and by the strength of the bond holding the atoms together (the stronger the forces holding, the harder a mineral is)Talc (softest) Diamond (hardest)Mohs relative hardness scale (10 steps)Minerals higher on the hardness scale have the ability to scratch any mineral lower than itself

12Moh's Hardness ScaleHardnessMineralDescription1TalcFingernail scratches it easily.2GypsumFingernail scratches it.3CalciteCopper penny scratches it.4FluoriteSteel knife scratches it easily.5ApatiteSteel knife scratches it.6FeldsparSteel knife does not scratch it easily, but scratches glass.7QuartzHardest common mineral. It scratches steel and glass easily.8TopazHarder than any common mineral.9CorundumIt scratches Topaz.10DiamondIt is the hardest of all minerals.13RememberIF the object scratchs the surface of the mineral, the mineral has a hardness less than that of the object

Mineral < Object

IF the mineral scratchs the surface of the object, the mineral has a hardness greater than the object

Mineral > Object

14MagnetismPlace a magnet up to the mineral, if there is an attraction than the mineral is magnetic.

15EffervescencePlace a small amount of cold, weak Hydrochloric Acid on the mineral sample.

If the sample bubbles white, then the mineral reacts to the HCl.

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Talc: H2Mg3(SiO3)4Colour- white, green, grayHardness- 1Streak- colorlessMagnetism- noLuster- vitreousHCl- no

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K-Feldspar: KAlSi3O8Colour- pink to whiteHardness- 6Streak- white/colorlessMagnetism- noLuster- vitreous to pearlyHCl- no

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Hematite: Fe2O3Colour- reddish or silveryHardness- 5-6Streak- reddishMagnetism- noLuster- metallic or earthyHCl- no19

Calcite: CaCO3Colour- variesHardness- 3Streak- white/colorlessMagnetism- noLuster- non-metallic/waxyHCl- yes20

Magnetite: Fe3O4Colour- blackHardness- 5.5-6.5Streak- blackMagnetism- yesLuster- metallicHCl- no21

Pyrite: FeS2Colour- brass yellowHardness- 6 6.5Streak- greenish blackMagnetism- noLuster- metallicHCl- no22Other PropertiesHere are a couple other properties used to identify minerals, but we will not be using themHowever, you should still understand HOW to use themCrystal Form and Growth HabitPlaner surfaces on ice intrigued Greek philosophers who applied the name crystals to any body that grows with a planer surfacePlaner faces are characteristic of every mineral however the number and angle of faces separates them apart from each other.It is this angle that gives each mineral a distinctive crystal form (internal order)

24Crystal Form and Growth Habit

CleavageThe tendency of a mineral to break in preferred directions along bright, reflective planer surfacesBroken fragments are bounded by cleavage surfaces that are smooth and planerDont confuse crystal faces with cleavage surfaces as cleavages are breakage surfaces whereas crystal faces are growth faces26

27Lab ActivityEach student is to fill out their own Worksheet, but can work in partners

5 minutes to test the physical properties of each mineral sample

After your time is up, I will let you know. Pass your mineral to the next group

Remember to look at the number on the mineral you are testing and fill it in the corresponding sections

HAVE FUN AND ASK QUESTIONS!!!

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