Introduction to Minerals Created By: Mr. Kreeger Homework and Page References Page References HW # on page 37 of text HW # on page 41 of text HW # 3- Explain what gives minerals their external features and how does their atomic structure affect this? Table of Contents 1. Minerals Defined a. Mineraloids b. Industrial Minerals c. Biochemical Minerals 2. Characteristics of Minerals 3. Crust Composition 4. Examples of Various Mineral Compositions 5. Crystalline Form Introduction to Minerals 1. Minerals Defined a. A mineral is the basic material that makes up the earths crust and has the following characteristics: 1. Naturally occurring 2. Inorganic 3. Has a fixed chemical composition 4. Has an orderly internal arrangement of atoms. 1. Minerals b. Mineraloids-Lack crystal structure (Examples include rare gemstones) c. Industrial Minerals- Used for manufacture of physical materials. d. Biochemical Minerals- Can be manufactured by organisms (Example: Aragonite-Made by clams to produce their shells) 2. Characteristics of Minerals a. Naturally Occurring- Formed as a result of natural processes in or on the earth b. Inorganic- Came from things that were never alive. c. Fixed Chemical Composition- Use of a chemical formula or symbol to represent what mineral is made of. 1. Some minerals found as pure elements (Cu, Ag), most are found as compounds (Calcite(CaCO3), Quartz(SiO2). 3. Composition of Crust Element% by Mass Oxygen46.40 Silicon28.15 Aluminum8.23 Iron5.63 Calcium4.15 Sodium2.36 Magnesium2.33 Potassium2.09 Nitrogen Hydrogen Other0.66 **98% of the crust is made of just 8 elements, even though there are over 100 known elements ( Pg 11 of ESRT) Composition of Crust 4. Examples of Various Mineral Compositions MineralChemical NameChemical Formula CalciteCalcium CarbonateCaCO3 GalenaLead SulfidePbS GypsumCalcium Sulfate-WaterCaSO2 +2H2O OlivineMagnesium SilicateMg2SiO4 K-FeldsparPotassium aluminum silicate KAlSi3O8 PyriteIron SulfideFeS2 QuartzSilicon dioxideSiO2 Pictures of Minerals Uses of Minerals 5. Crystalline Form a. Atoms or molecules of a mineral are the same throughout that mineral b. There is a definite repeating pattern in minerals, if pattern is large enough to be seen it is called a crystal. c. Internal structure determines outside structure. 5. Crystalline Form Cont. d. The shape of the minerals crystals as a result of its atomic arrangement Introduction to Identifying Minerals Use your Earth Science Reference Tables (ESRT) page 16 when identifying an unknown mineral! 6. Identifying Minerals There have been over 2000 minerals identified. They can be classified by both physical and chemical properties. 7. How to Identify Minerals a. Color- First property usually observed. Very unreliable way to identify minerals Many minerals come in a variety of colors (Quartz) Some minerals have same color (Pyrite (FeS2) and Gold (Au)) Due to impurities The many colors of Fluorite 7. Identifying Minerals b. Luster- The way a mineral reflects light from its surface. Nonmetallic-Glassy, brilliant, greasy, oily, waxy, silky or earthly. Metallic- Has metallic properties 7. Identifying Minerals c. Streak- This is the color of the fine powder left when a mineral is scratched against an unglazed ceramic tile. Even if color of mineral changes (Quartz) the streak is always the same. (This is a very reliable way to identify minerals) 7. Identifying Minerals d. Hardness- The ability for a mineral to resist being scratched. The hardness of a mineral is usually stated in terms of Mohs scale of hardness A harder material can always scratch a softer material but a softer one cant scratch a harder one. HANDOUT 7. Identifying Minerals e. Cleavage- The tendency of a mineral to break parallel to atomic planes in its crystalline structure. Ex. Mica- Breaks in parallel layers 7. Identifying Minerals f. Fracture- When minerals break unevenly because all planes are equally strong in all directions. a. Conchoidal- Smooth, curved break that looks like a shell b. Fibrous or splintery- Fibers c. Hackley- Jagged sharp edges (Native Metals) d. Uneven Mica Halite Galena, Pyrite Calcite Feldspar Fluorite 8. Alternate ways to Identify Minerals a. Specific Gravity- This is a ratio off the density of a mineral compared to the density of water. (NO UNITS) b. Chemical Tests- Use of HCl tests for calcium carbonate, if mineral contains it will bubble or effervesce. (Calcite, Dolomite) 8. Alternate ways to identify Minerals c. Magnetism- Minerals that contain iron, copper or nickel will attract a magnet. 9. Major Mineral Groups a. Silicates- One ion of silicon is attached to 4 ions of oxygen in the shape of a tetrahedron. Bonds are strong. b. Sulfides- When 1 or more sulfur ions combine with a metallic ion (PbS, FeS, ZnS) 9. Major Mineral Groups c. Oxides-Compounds in which Oxygen is joined with ions of other elements, usually metals. (Fe2O3,FeO). d. Carbonates and Sulfates- Minerals contain Oxygen, the oxygen ion join with other ions to form polyatomic ion Carbonate ion (CO3)^-2 Sulfate ion (SO4)-2 HANDOUT Final thoughts about Minerals Remember Your ESRT pg 16 lists all the mineral information you will need to identify an unknown mineral sample!