Minerals Ms. Rudisill

What is a mineral? 1. Made up of elements in the earth’s crust! 2. Minerals must have the following 5 characteristics: Occurs naturally Solid Definite chemical composition Atoms are arranged in an orderly pattern – crystal Inorganic

3) 8 elements make up 98.5 % of the earth’s crust Oxygen and Silicon are the most abundant 90% of ALL minerals are made with Oxygen and Silicon 4) Most Minerals are compounds Halite – NaCl Quartz – SiO2 5) A few minerals are single elements, native elements Silver – Ag Diamond - C

How Do minerals form? 1. Magma – molten rock a) Atoms in magma solidify b) Magma starts to cool c) Atoms move close together and form compounds d)Types of minerals that form depend on the type and amount of elements in the magma e) Cooling time determines size of minerals Long cooling time = large minerals Short cooling time = small minerals

3) Pressure A rock is put under great temperature and pressure Minerals begin to break down chemically Pressure becomes great enough to change the minerals without melting them. Atoms recombine forming new minerals Minerals grow in opposite direction from the pressure.

4)Water a) Evaporating saltwater -bodies of saltwater evaporate -As saltwater evaporates the minerals crystallize -Ex: Gypsum and Halite b) Surface and groundwater -Surface and groundwater carry dissolved materials into lakes or seas -Dissolved minerals settle on the bottom of the lake or sea -Ex: Mica

c) Hot-water Solutions -Groundwater makes its way through the ground in Earth’s surface -Magma inside Earth mixes with the water -Water evaporates and causes the dissolved metals and other elements to precipitate out of the water -ex: gold, copper, sulfur, pyrite, and galena

Mineral resources Source of metals - Ores Gemstones/Jewelry Abrasives Fertilizer Glass

Identifying minerals observable properties Color Luster – the way a mineral shines in light Crystal Structure Crystal size is determined by the amount of time it has had to cool. Long cooling time creates large mineral crystals Short cooling time creates small mineral crystals

Property of Color Some minerals have distinct colors Many minerals have similar colors Some minerals have many colors Some minerals change colors

Identifying minerals testable properties Streak Color of a minerals powder Obtain streak by rubbing the mineral on an unglazed white tile (streak plate). Color of the mineral may vary, but the streak is always the same Streak Rules Streak of a metallic mineral is at least as dark as the mineral Streak of a nonmetallic mineral is usually colorless or white

Property of luster Metallic – shines like polished metal Nonmetallic – may be shiny but not like a metal Vitreous – like glass; Quartz Pearly - Mica Adamantine- hard brilliant luster; Diamond Greasy Oily Dull Earthy

Crystal structures Crystal is an orderly arrangement of atoms in a mineral All minerals have a crystal structure, but you cannot always see the structure. Six Crystal Systems Cubic Orthorhombic Tetragonal Hexagonal Monoclinic Triclinic

Crystal structures

Identifying minerals testable properties Cleavage Tendency of a mineral to split easily along flat surfaces. Useful because cleavage surfaces can be observed even on tiny mineral grains. Fracture When minerals break in directions other than along cleavage surfaces. Conchoidal Fracture – surface is smooth and curved like the inside of a clam shell Splintery Fracture – Jagged surface with sharp edges Irregular Fracture – leaves generally rough surfaces

Identifying minerals testable properties Hardness Resistance to being scratched Use the Mohs Scale of Hardness Scale was created by Friedrich Moh Scale goes from 1 (softest mineral) to 10 (hardest mineral) Determining Hardness If a mineral can be scratched by an object than it is softer than that object. If a mineral is not scratched by an object than it is harder than that object

Identifying minerals testable properties

Mohs’ Scale of Hardness Mineral Simple Test Talc Fingernail scratches it easily Gypsum Fingernail scratches it Calcite Copper Penny scratches it Fluorite Steel knife scratches it easily Apatite Steel knife scratches it Feldspar Steel knife does not scratch it, it scratches window glass easily Quartz Hardest common mineral; it scratches steel and hard glass easily Topaz Harder than any common mineral Corundum It scratches Topaz Diamond Hardest of all minerals

Identifying minerals testable properties Fluorescence – minerals that glow under ultraviolet light. Magnetism – magnetic Acid Test – mineral reacts when in contact with Hydrochloric (HCl) acid. Specific Gravity Ratio of its mass to the mass of an equal volume of water. Tells you how many times denser the mineral is than water.

Identifying minerals testable properties Double Refraction Iceland Spar Calcite Causes single object to appear as two objects when viewed through the calcite Taste – Example Halite has a salty taste

Possible Other Properties Salty Taste Double Refraction Magnetic Heavy Greasy (smudges on fingers and paper) Flakes apart 6-sided crystal (you might have two of these!) Almost perfect square/rectangle pieces Feels soft like powder!

Mineral Groups Minerals are divided into two groups based on the elements they are composed of. Silicate Minerals Minerals that contain a combination of silicon and oxygen Silicate minerals can still contain other minerals, but are made up mostly of Silicon and Oxygen. Nonsilicate Minerals Minerals that do not contain a combination of the elements Silicon and Oxygen These minerals may have one of these minerals