UNIT II Rocks, Minerals, & Resources Mineral Display at American Museum of Natural History in NYC Presentation created by Mr. Elliott from Fort Plain Central School. Modified by Mr. Oliver Summer 2012. Start Unit II Objective Page Don’t forget to leave a column for dates. • #1. What are minerals and describe their characteristics? • #2. Describe properties of minerals including the seven basic physical properties of minerals. (ESRT p.16) Introduction • Lithosphere – includes crust and small portion of upper mantle – Made of solid materials called rock. • Building blocks of rock are called minerals. • Rocks composed of single mineral called monomineralic. • Rocks composed of many minerals called polymineralic. Monomineralic Rock Rock Salt Polymineralic Rock (made of halite only). A. Minerals • *Mineral:Naturally formed material made up of one or more elements. In order for a material to be a mineral it must be (have): _________________________Naturally occurring _________________________Inorganic (not from a living thing) _________________________Crystalline _________________________Solid material with definite shape _________________________Definite Molecular structure _________________________Specific physical properties There are over 2,400 minerals that have been identified on Earth! Of these, there are about a dozen of them that are so abundant that they make up more than 90% of the Lithosphere. These very abundant minerals are called the “rock formers”. •Minerals are made up of elements. •Element: A substance composed of atoms which can not be broken down into a more simple substance. •Some minerals are made up of only one element but most are made up of two or more elements and are called compounds. Diamond (only 1 element carbon) Halite (compound) *Native Element Minerals: Minerals that occur in nature as single elements. (Ex. Gold, iron, graphite, diamond, sulfur) ESRT p.16 Chart from cover (p.1) of ESRT Be careful as % by mass and volume aren’t the same! *A Minerals physical properties are determined by its: Internal arrangement of atoms! aka: bonding or atomic structure Internal structure of Halite Mineral Review II. Physical and Chemical Properties The identification of minerals is done on the basis of well defined physical and chemical properties Physical Properties: ________________Things you can see. Chemical Properties: _____________________________How a certain substance reacts with other______________ substances. Also includes: ________________________________Things associated with atomic structure. Carbon Atoms Silica Tetrahedron (Graphite and Diamond) *A. Color: Unreliable for two reasons: 1. Different_______________________________ minerals are the same color. • Ex: Halite______________ and calcite 2. _____________________________One mineral may have many colors. Only a small impurity can easily change the mineral color. • Ex: ______Calcite or classroom samples of quartz * B. Streak: _______________________________The color of a mineral in powder form. • We do a streak test using a __________Streak plate (an unglazed piece of porcelain tile) Note: The color of a mineral may be very different than the streak. Streak is: _______________________More reliable than the color. * Streak (not listed for all minerals) * C. Hardness: __________________________________Resistance of a mineral to being scratched. • A hard mineral will make a scratch on a softer mineral • To compare the hardness of minerals, scientists have developed a scale called the: __________________Moh’s scale of hardness. • This scale also: ________________________________compares hardness of common objects (Iron nail) (Feldspar) (Streak plate) D. Luster: _________________________________________The appearance of light reflected from a mineral’s _______surface. • Luster can either be metallic or nonmetallic. a) Metallic: _________________________If a mineral shines like a metal. • Ex: ________________________Galena, Magnetite, and Pyrite b) Nonmetallic: _______________________________If a mineral does not look like a metal. • Ex: __________________________________Glassy, Waxy, Greasy, Earthy, Dull, etc… Examples of Nonmetallic Luster Earthy Glassy Waxy Dull E: Cleavage vs. Fracture Cleavage: The tendency of a mineral to break along zones of weakness or flat sides. These zones of weakness appear as smooth planes or surfaces. Fracture: breaking unevenly, no definite cleavage. Beryl (Aquamarine) Remember: If a mineral breaks Basal Cleavage evenly with cleavage or unevenly Cubic Cleavage (One directional) with fracture depends on the (three directional Ex: Mica internal arrangement of its atoms. at right angles) Ex: Halite Rhombic Cleavage (three directional not Conchoidal Fracture at right angles) Ex: Obsidian Ex: Calcite * F. Crystal Forms: The________________________________ geometric shape of a mineral due to its _______________________________internal arrangement of atoms. * G. Specific Gravity: _____________________________________The ratio of the density of a mineral compared ___________________To the density of water g •The Density of pure water is 1 /cc . •So, if a mineral had a specific gravity of 3, the density of the g mineral would be: 3____. /cc What is going on mathematically? g 3 /cc g g = 3 /cc = 1 /cc g 3 1 /cc Divide density Units cancel Specific gravity of mineral by of mineral density of water So specific gravity is just like density, but with no units… H) Special Properties of Some Minerals Calcite Reacts with Acid: When HCl is placed on a clean surface, it gives off bubbles of CO2 . Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas) Halite tastes like salt Magnetite exhibits magnetic properties. Talcum Powder Talc feels slippery. Fluorescence: Mineral emits visible light when illuminated with high energy light (ultraviolet). Phosphorescence: Mineral emits visible light even after ultraviolet light is switched off. (glows in the dark.) a) Minerals are crystalline. • Crystalline- atoms inside are bonded in a particular pattern or structure – Depends on “internal arrangement” of atoms • Two minerals with the same chemical composition but different crystal structure may have very different properties. Diamond • Examples: – Graphite and Diamond • Both made of pure Carbon • Different Bonding • Graphite-weak bonds, very soft, used in pencils • Diamond-strong bonds, very hard, jewelry/sawblades Graphite • Another Example: – Sand and Quartz or Glass • Both composed of SiO2 • Different bonding, very different properties Quartz Quartz Sand b) Minerals may be grouped according to the elements of which they are made, or the compounds which they can form. • Examples: – Oxides- oxygen with another element – Carbonates- metal combined with CO3 (carbonate formula) – Silicates- silicon bonded with oxygen • Silicate formula- SiO4 • Silicate building block- tetrahedron Calcium carbonate (limestone) Iron oxide (rust) Cover of ESRT’s The two most abundant elements in Earth’s crust by mass and volume are? How many minerals in your ESRT’s contain both? ______________mineralsSilicate are the most common on Earth! Igneous Rock Objectives • #3. How are igneous rocks formed? (ESRT p.6) • #4. Describe how igneous rocks can be classified according to either mineral composition or where they were formed. (ESRT p.6) • #5. Explain how igneous rock texture is related to crystal size. (ESRT p.6) 3 Families of Rocks • Igneous • Sedimentary • Metamorphic Let’s start first with the mother of all rock families…. Igneous – Latin igneus, from ignis fire “Of, relating to, or resembling fire.” Source: Merriam-Webster B1 Igneous Rocks 1. Igneous Rocks: Form from the solidification and/or crystallization of liquid or molten rock ____________:Magma Molten rock underground. ____________:Lava Molten rock above ground. ____________:Solidification The process of becoming a solid igneous rock. Crystallization____________: Cooling of magma or lava creates crystals. Mineral crystals may form resulting in the igneous rock having a crystalline texture. ***Crystals within a rock are a good indicator of an igneous origin. II. Igneous Rock Texture and Crystal Size The texture of the igneous rocks (size of the crystals) is dependent upon the rate of cooling. If molten rock cools slowly the crystals will be LARGE. _______LARGE crystals mean ______coarse texture (_________).Phaneritic If molten rock cools rapidly the crystals will be small. Small crystals mean fine texture (Aphanitic). Vesicular rocks are created when gases remain trapped in a quickly cooling rock. Air pockets, called vesicles, are the visible evidence. Ex: Scoria When molten rock is quenched (cooled extremely fast), no crystals form and is said to have a glassy texture. Ex: obsidian Graph showing relative rate of cooling vs. crystal size of igneous rocks Large Crystal Size Crystal Small Slow Fast Rate of Cooling III. Environment of Formation: _____________________.Where the rock solidified Intrusive: _______ Plutonic rocks produce _____________________Large (1 mm and larger) crystals due to slow underground cooling from magma Extrusive: ________Volcanic rocks produce ___________________Small (less than 1 mm) crystals because lava cools faster near or on Earth’s surface Intrusive igneous rock: Deep Underground Extrusive igneous rock: Near or on Earth’s Surface IV. Composition: The___________________________________. type of minerals that make up the rock Rocks that are: Felsic : ____________________________Light in color, low in density, _______________.high in Aluminum Mafic