Ch 5- Minerals

Minerals Ch 5, p. 103 QOD- What is a mineral?

 Question set- #1-10 today. Show me when you finish 1-10 and then keep in notebook.  REMEMBER: LAB TOMORROW! –Missing contracts –Shoes & Lab Safety Rules

Sep 14  QOD- What are the seven physical properties used to identify minerals? 1.Review of Identifying Metals Lab 2.Video Clip- Minerals 3.Notes & Questions- ch 5 minerals 4.Keep the questions in your notebook 5.Test 4 – 5 Wednesday

Sep23 Earth Systems  Test- chapters 4 & 5 is Thursday!  Today- –Ch 5 notes  Tomorrow- –Last day to turn in mineral projects  Wednesday: Crystal Growing-! –Bring 1 pound (2 cups) sugar –Wear close toed shoes  Thursday- test ch 4-5

Is it a Mineral?  Is it inorganic?  Does it occur naturally?  Is it a crystalline solid?  Consistent chemical composition?  Must answer yes to all 4 questions for it to be a mineral

10 Most common minerals  Quartz  Calcite  Orthoclase  Dolomite  Plagioclase  Halite  Muscovite  Gypsum  Biotite  Ferromagnesian minerals  These make up 90% of Earth’s mass

Mineral Groups  Silicates –96% of Earth’s crust –Contains Si (silicon) and O(oxygen) quartz –Can have other elements also –Feldspar –  Orthoclase if K (potassium),  Plagioclase if Na (sodium) or Ca (calcium) –Ferromagnesian minerals – rich in Fe (iron)

Orthoclase - LorenzenitePlagioclase - Albite Ferromagnesian - Olivine

Mineral GroupsMineral Groups  Nonsilicate Minerals –Do not contain Si and O  Can contain one or the other, but not both –Six groups  Carbonates  Native elements  Halides  Oxides  Sulfates  Sulfides

Carbonate - Calcite Halide - Halite Native Elements - Gold Oxides - Hematite Sulfates - Gypsum Sulfides - Galena

Crystalline Structure  Crystal – atoms, ions, or molecules are arranged in a regular, repeating pattern  Silicate crystal structure –Silicon – oxygen tetrahedron –1 Si with 4 O’s around it (illustrated in the book) –Basic building block of silicates –Can be connected 6 different ways

Silicate Tetrahedron

Crystalline Structure  Nonsilicate crystals –Diverse chemical composition leads to variety of crystal structures –Cubes, hexagonal prisms… –Crystal structure influences physical properties  Native elements are dense due to compact crystal structure

Physical Properties of Minerals  Mineralogist –Examine, analyze, and classify minerals  Result from chemical composition and crystal structure  Can be useful in identifying minerals

Physical Properties 1)Color Not reliable for ID purposes (subjective)Not reliable for ID purposes (subjective) Small amount of impurities can affect colorSmall amount of impurities can affect color Weathered surfaces may hide colorWeathered surfaces may hide color Only look at fresh surfacesOnly look at fresh surfaces

Color

Physical Properties 2)Streak Color of mineral in powder formColor of mineral in powder form Streak plate – unglazed ceramic tileStreak plate – unglazed ceramic tile Streak color may differ from mineral colorStreak color may differ from mineral color Metallic minerals – darker streakMetallic minerals – darker streak Nonmetallic minerals – lighter streakNonmetallic minerals – lighter streak

Streak

Physical Properties 3)Luster  Light reflected from mineral’s surface  Metallic luster – shiny surface  Nonmetallic luster  Glassy  Waxy  Pearly  Brilliant  Dull / Earthy

Metallic Luster

Glassy Luster Quartz

Waxy Luster Variscite

Pearly Luster Talc

Brilliant Luster Diamond

Dull / Earthy Luster Psilomelane

Physical Properties 4)Cleavage / Fracture –Cleavage  Splitting along specific lines of weakness  Forms smooth, flat surfaces –Fracture  Break unevenly into pieces  Forms curved, irregular surfaces  Conchoidal fractures – curved surface

Cleavage - Calcite

Fracture Conchoidal

Fracture Irregular

Physical Properties 5)Hardness  Ability to resist scratching  Mohs Hardness Scale  Scale of 1 to 10  1 = Talc10 = Diamond  Glass is about a 5

Mohs Hardness Scale

Physical Properties 6)Crystal Shape –6 Basic shapes –Certain minerals always form crystals with the same shape 7)Density –Ratio of mass to volume –Can help identify minerals

Crystal Shapes

Physical Properties  Fluorescence and phosphorescence  Chatoyancy and asterism  Double refraction  Magnetism  Radioactivity

Diamond fluorescence with ultraviolet light Phosphorescence – over time on a watch face

ChatoyancyAsterism

Double Refraction

Crystal Growing Lab- Wedn.  Bring 1 pound (2 cups) sugar  Wear close toed shoes