Chapter 3 MineralsSection 1 Properties of Minerals
Where do we find minerals? Museums Jewelry Building Materials (glass and steel are made from minerals!) Graphite (in your pencil) Food (iron and sodium are important minerals in our diet!) Caves Rocks!
How do we get minerals? We have to extract minerals from within the Earth’s crust by mining. “minare” – means to mine.
What is the definition of a Mineral? To be considered a mineral something must be….. 1. Naturally Occurring 2. Inorganic- it does not form from the remains of living things. 3. Solid 4. Crystal Structure- Atoms in a mineral line up in a repeating pattern forming a crystal. Crystals have flat sides called faces and geometric angles. 5. Definite Chemical Composition- Minerals can be made of elements or compounds.
More on Definite Chemical Composition…. •Minerals can be pure elements or compounds. •Example: Sulfur (S) is a pure element (made only of 1 type of atom) in the crust. It is also a mineral. •Example: Pyrite (FeS2) is a combination of elements, so it is a compound, but it is also a mineral. •Pyrite is Fools Gold!
There are over 3000 minerals! In fact, 90% of Earth’s crust is made of minerals.
Silicate Minerals Most of the minerals in the crust are called Silicate minerals. (minerals containing Silicon, Si and Oxygen, O) Mica (KAl2(AlSi3O10)(OH)2), Talc (H2Mg3(SiO3)4), Quartz (SiO2)
Let’s learn to identify some minerals… Now that you know something about physical properties and mineral formation, let’s identify some minerals.
How to Identify Minerals There are eight things you can look for to identify minerals.
How to Identify Minerals1. Color Sometimes you can identify a mineral by its color. Sometimes you cannot because it may come in a variety of colors and there are many minerals that have the same color.
Example: The mineral quartz is often thought of as clear but it can also be the following colors: amethyst (purple), citrine (yellow- brown), agate (multicolored), aventurine (green), smokey quartz (gray), rose quartz (pink)
How to Identify Minerals 2. Streak The streak is the color of the mineral’s powder. It may be different from the color of the mineral. You test the streak of a mineral every day. What mineral is this? Graphite!
How to Identify Minerals3. Luster- how much light is reflected from the surface. How “shiny” a mineral is. Quartz has a glassy luster Galena has a metallic Luster
How to Identify Minerals 4. Crystal Form Sometimes crystals are obvious, other times they can only be seen through a microscope.
The crystals of each mineral ‘grow’ atom by atom to form that mineral’s particular crystal structure. Geologists classify these structures into groups based on the number and angle of the crystal faces.
5. Hardness Moh’s Hardness Scale rates a mineral’s hardness. “1” being the softest and “10” being the hardest. Some minerals are ‘harder’ than others or can ‘scratch’ other minerals. A Diamond is the hardest known substance on the planet so it can scratch any other mineral!
6. Cleavage or Fracture This describes how a mineral breaks. If a mineral has cleavage, it usually has smooth sides that resemble the original shape of the mineral. Example: Mica If it fractures, it is irregular and jagged or rough. Example: Quartz
7. Density Density is a measurable property of a mineral. It will also make a mineral feel heavy or light.To calculate density: D=m v
8. Special Properties There are numerous special properties which help identify minerals. This mineral (Fluorite) glows under a black light! Magnetite is naturally magnetic. Magnetite or “Lodestone” was used by Vikings more than 1,000 years ago as compasses Sulfur smells like rotten eggs. Calcite fizzes when acid is
Section 2: Mineral Formation How do minerals form?
Lets Review… What Is a Mineral? A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition.
Crystallization All minerals must form through crystallization. Crystallization is when atoms are arranged to form a material with a crystal structure.
Minerals Crystallize in 2 Ways…1. Cooling of certain materials : a. When Magma/ Lava Cools - magma is beneath the earth’s surface and lava is above. b. When a hot water solution containing dissolved elements and compounds cools, the atoms begin to arrange into crystals.2. Evaporation of a Solution – When a solution contains minerals that are dissolved, if the water evaporates the minerals will crystallize and ‘come out of solution’.
Minerals Crystallize in 21. On the earth’s surfacePlaces… a. through evaporation or cooling of solutions containing dissolved minerals, elements, or compounds (seawater). b. when lava cools and hardens.
Examples: Table Salt (NaCl) formed as ancient shallow salty seas slowly evaporated. Gypsum is another mineral that forms from evaporation of seawater. It is used in drywall.
Petrified Wood Petrified Wood is wood that has been fossilized by being turned into minerals. This occurs when the wood soaks in water containing dissolved minerals over a long period of time. As the water evaporates, the minerals will crystallize in every space of the wood, or the water dissolves the original wood and mineral crystallization completely replaces it. Eventually, the mineral forms a perfect copy of the wood, including cell structure and fibers! The replacement mineral is usually a variety of quartz. Petrified wood may be colored by chemical impurities such as iron and copper. There are entire forests that petrified! When trees become uprooted, deposited in water, and covered by mineral-rich mud or volcanic ash, petrified forests can form. The age of petrified wood varies from place to place, but generally speaking most samples are hundreds of millions of years old! T
Minerals Crystallize in 2 Places…2. Beneath the Earth’s Surface/Underground a. hot groundwater with dissolved minerals cools b. when magma cools and hardens
Examples: Minerals can be extracted from the veins in the rock. A vein forms when hot ground water (heated by magma) containing dissolved minerals travels through rocks, cools, and the minerals crystallize. Gold and Silver can be extracted from veins in rocks.
Examples… A geode is a rounded hollow rock lined with mineral crystals inside. A geode forms when hot water containing dissolved minerals seeps into a crack or hollow rock and cools.
Deep Underground=Slow Cooling = Large Crystals Minerals that have large crystals Minerals that have large crystals do so because magma or a hot water solution is cooling SLOWLY deep below the earth’s surface. When temperatures are high, cooling occurs slowly and the crystals are large and it is easy to see the flat, smooth sides and geometric angles. Extreme Example: Selenite (Gypsum) crystals that formed from a hot water solution cooling slowly in a deep cave in Mexico below earth’s surface for 500,000 years! http://www.youtube.com/watch?v=wgUFb_l4DLE
At or near Earth’s Surface=Fast Cooling=Small Crystals Minerals that have small or microscopic crystals do so because hot water solutions, magma, or lava cool at or near the earth’s surface When temperatures are low, cooling occurs fast, and crystals are fine, sometimes too small to see at all. Remember, Fast is Fine!
Size and Available Space Minerals that have large, perfect crystals have had a long time to ‘grow’ through slow cooling, but they also have had a lot of room (such as in a cave) to ‘grow’ large and perfect.
Section 3: Using MineralUses of Minerals: Resources Gemstones and jewelry Metals-examples: Aluminum, Copper, Iron, Silver Quartz is used in glass making Talc is ground up to make baby powder and is a main ingredient in eye shadow and powdered makeup. Diamonds, the hardest known mineral, are used in drill bits and saws. Fun fact: Small pieces of mica used to be used as glitter! (now it is made of pieces of plastic and foil.)
Producing Metals from Minerals To produce metal from a mineral, a rock containing the mineral must be located through prospecting and mined, or removed from the ground. Then the rock must be processed to extract the metal. A mineral that contains a metal that can be mined and sold at a profit is called an ore. Iron ores: Magnetite (Fe3O4) and Hematite (Fe2O3)
Producing Metals from Minerals A prospector is anyone who searches for an ore deposit. Geologists prospect for ores by observing rocks on the land surface and by studying maps of rocks beneath the surface.
Mining2. Open Pit Mining-giant pit dug to remove ore. Open Pit Copper Mine, Utah3. Shaft Mines-network of tunnels dug deep in the ground to extract ore from veins. Shaft Mine
Smelting is a process which Ore Processing-Smelting removes the useful metal Example: Iron Ore from an ore. In iron ore smelting, a blast furnace is filled with iron ore, coke (baked coal) and limestone (CaCO3). Huge quantities of hot air blast in at the bottom of the furnace, causing the coke to burn, forming CO2 gas and liquid iron. The liquid iron collects at the bottom of the blast furnace. Any impurities left in the ore combine with the limestone to make the waste product slag, Iron ores: Magnetite (Fe3O4) and which settles above the iron. Hematite (Fe2O3)
Have you heard of the “Hot- Metal” Bridge? Once the iron was in a hot metal car, the Hot Metal Bridge in Pittsburgh moved the iron by rail from the Eliza furnaces along the Mon River to Pittsburghs South Side to produce finished steel.
Carrie Furnaces, which were part of Homestead Steel Works, are near the Waterfront in Pittsburgh. They were also the site of smelting to produce iron which was used to make steel.
Alloys After smelting, sometimes other materials are added to the metal to make an alloy. An alloy is a mixture of 2 or more elements and has the properties of a metal. Steel is an alloy made of smelted iron (further purified by the Bessemer process) and some carbon. The addition of carbon makes steel harder and stronger than iron. Adding the metal Manganese to steel produces even stronger steel. Adding Chromium and Nickel to steel produces stainless steel.
Edgar Thomson Steel Works is a steel mill in NorthBraddock, Pennsylvania originally built by AndrewCarnegie. You can see it from Kennywood! It has 2 blast furnaces still in operation used to smeltiron ore and then produce finished steel.