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Properties of MineralsProperties of Minerals
What are minerals?What are minerals?
• There are over 3000 minerals.
• Roughly 100 common minerals
• A mineral is a naturally occurring, inorganic solid that has a crystal structure and definite chemical composition.
5 Characteristics of Minerals5 Characteristics of Minerals
• Naturally Occurring
• Inorganic
• Solid
• Crystal Structure
• Definite Chemical Composition
Naturally OccurringNaturally Occurring
• Formed by geological processes not man.
• Ex: Copper is a mineral but steel is not because it is made by man.
InorganicInorganic
• A mineral cannot be made from a material that was once a part of a living organism.
• Ex: Oil and coal form naturally in the Earth’s crust, but form from the remains of animals and plants from millions of years ago.
SolidSolid
• A mineral has to be solid with a definite shape and volume.
• In a solid the molecules are packed tightly so they cannot flow freely, so the object keeps it’s shape.
Crystal StructureCrystal Structure
• A mineral is made up of a pattern that continually repeats
• The repeating pattern of a mineral’s particles forms a solid called a CRYSTAL.
• Sometimes you are able to see the crystal with the naked eye other times you must use a microscope.
• Opal is considered a mineral even though their particles are not arranged in a crystal structure.
Definite Chemical CompositionDefinite Chemical Composition
• A mineral has a definite chemical composition.
• Meaning: Minerals contain certain elements in definite proportions.
• Almost all minerals are compounds: made of 2 or more different elements bonded together.
• Some minerals are made of one element: Examples are gold, silver, and copper.
Element, Compound, MixtureElement, Compound, Mixture
• Mixture: is a substance composed of two or more substances that re mixed together but not chemically.
• Each substance in a mixture keeps their separate properties. Example: Salt Water
• Element: a substance composed of one type of atom. Each element has unique chemical and physical properties.
• Compound: is a substance composed of two or more elements where the elements no longer have distinct properties.
• Each compound has it’s own properties that differ from the properties of each element.
Identifying MineralsIdentifying Minerals
• Gold Rush: COLOR ALONE WILL NOT WORK!
• Each mineral has its own unique physical properties that can be used to identify it.
• The following characteristics can be used to identify minerals:– Hardness Color Streak– Luster Density Crystal Systems– Cleavage/Fracture Special Properties
ColorColor• Very simply what is the color of the
mineral.
• This can be easily seen however color can only be used to identify a few minerals because only a few minerals have their own characteristic color.
• For example azurite is always blue.• Some minerals like quartz are found in
several colors.
StreakStreak• The streak of a mineral is the color of its powder.
• You can determine this by rubbing a mineral against a piece of unglazed tile called a streak plate.
• The color of a mineral may vary, but its streak will not.
– Pyrite: Gold color Greenish black streak– Gold: Gold color Yellow streak
LusterLuster• This term is used to describe how a mineral reflects
light from its surface.
• Minerals containing metals are often shiny.
• Ex: Galena: Metallic Luster
• Some of the terms used to describe a non-metallic luster in minerals:– Glassy, earthy, waxy, pearly, silky.
HardnessHardness
• How hard a mineral is an excellent tool for identifying the mineral.
• MOHS HARDNESS SCALE was invented to test and compare the hardness of different minerals.
• The scale ranks 10 minerals from softest to hardest.
Hardness (continued)Hardness (continued)
• A mineral can scratch any mineral softer than itself and it will be scratched by any mineral harder than itself.
Mohs Hardness ScaleMohs Hardness ScaleMohs Mineral Hardness Example Other Mineral Talc 1
1.5 GraphiteGypsum 2 “
2.5 Fingernail “ Calcite 3 Copper coin Fluorite 4 Apatite 5 Steel nail
5.5 Glass plate Orthoclase 6
6.5 Steel file Quartz 7 Garnet Topaz 8 Corundum 9 Diamond 10
DensityDensity
• Each mineral has a characteristic Density.
• Density = Mass / Volume (remember the heart)
Crystal SystemsCrystal Systems
• Crystals of each mineral grow atom by atom to form that mineral’s particular crystal structure.
• There are 6 groups/ mineral structures:• Cubic Hexagonal Tetragonal • Monoclinic Triclinic Orthorhombic
CleavageCleavage
• A mineral that splits easily along flat surfaces has this property.
• Cleavage is determined by the arrangement of atoms inside the mineral.
• Depending on the arrangement minerals may split more easily in one direction than another.
FractureFracture
• Fracture describes how a mineral looks when it breaks apart in an irregular way.
Special PropertiesSpecial Properties• Some minerals have special properties
such as FLUORESCENCE.
• These minerals will glow under fluorescent light.
• Some minerals are magnetic. Ex: Lodestone
Special PropertiesSpecial Properties
• Calcite fizzes and gives off Carbon dioxide when you drop acid on it.
• Quartz has electrical properties:– If pressure is applied to these crystals a small
electrical current is produced. Because of these properties, quartz crystals are used in watches, microphones, etc.