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Minerals
Chapter 3
What is a Mineral?
Mineral Characteristics
Naturally occurring Inorganic Solid Definite chemical composition
Either elements or compounds Have orderly arrangements of
atoms Crystalline/Set atomic pattern
The Structure of Minerals Crystals Solids in which the atoms are
arranged in orderly, repeating patterns. Minerals are classified into six
major crystal systems according to their crystal structures: Hexagonal Cubic Tetragonal Orthorhombic Monoclinic Triclinic
The Structure of Minerals Formation of
Crystals:
From the cooling and solidification of magma The type and amounts of elements
present in the magma partly determine which minerals will form.
How rapidly the magma cools determines the size of the crystals. Slow – large Fast – little
From the evaporation of a solution or the supersaturating of a solution
Mineral Compositions and Groups Mineral
Classification
2 Main Groups: Silicates
Minerals that contain silicon and oxygen
Contain most of the common rock-forming minerals
Nonsilicates Do not contain silicon
Mineral Compositions and Groups Mineral
Amounts:
About 4,000 different mineral are found on Earth. Only a few dozen of these minerals
are common. 90 elements occur naturally in
the crust of the Earth. ~98% of the crust is made of only
eight elements. Silicon and Oxygen are two of
the most abundant elements found in Earth’s crust.
Identification of Minerals Hardness A measure of how easily a
mineral can be scratched Measured on a scale of 1 to 10
called the Mohs Scale. 10 = hardest, diamond 1 = softest, talc Iron nail = 4.5 Fingernail = 2.5
Identification of Minerals Luster The way a mineral reflects light.
Metallic or nonmetallic
Identification of Minerals Specific
Gravity
Ratio of the weight of the mineral with the weight of an equal volume of water.
Specific gravity of minerals can be roughly relatively tested using heft.
Identification of Minerals Streak Color of a mineral in a powder
form Found by rubbing the mineral
across a porcelain streak plate
Identification of Minerals Cleavage Mineral breaks along smooth,
flat surfaces Due to the atomic arrangement of
the mineral
Identification of Minerals Fracture Fracture
Mineral breaks along rough, uneven, or jagged surfaces.
Identification of Minerals Color and
Appearance
Color and Appearance Highly unreliable.
Identification of Minerals Other
Properties
Other properties Magnetic Optics Chemical reactions
Gems Properties of
Gems
Gemstones are highly prized minerals because they are rare and beautiful. Most gems are special varieties of
a particular mineral. Clearer, brighter, or more colorful Have a slightly different chemical
formula: Amethysts are quartz with a trace
amount of iron. Have a better crystal structure.
Gems Important
Gems
Cullinan Diamond Largest uncut diamond discovered Found in South Africa in 1905 3,106.75 carats (621 g) Cut into 9 main stones and 96 smaller stones Largest of these, the Great Star of Africa
(530.20 carats) is part of the British crown jewels.
Hope Diamond Purchased by Henry Philip Hope around 1830. 45.52 carats (9 g) All Hope’s family plus a later owner suffered
misfortune. Currently on display in the Smithsonian.
Gems Useful Gems Diamonds
Used as industrial abrasives and cutting tools
Rubies Produce certain types of laser light
Quartz Used in timepieces and electronics
Useful Elements in Minerals Ores A mineral or rock that contains a
useful substance that can be mined at a profit Examples:
Iron is found in the ores hematite and magnetite
Aluminum is found in the ore bauxite
Useful Elements in Minerals Extracting
Elements
Refining Wanted element is separated from
unwanted materials. Smelting
The substance is melted to separate it from any remaining unwanted materials.
Useful Elements in Minerals Vein Minerals Occur when dissolved metallic
elements travel in fluid form through weaknesses in rock and form mineral deposits.
Useful Elements in Minerals Titanium Found in ilmenite and rutile.
Lightweight and durable Used in auto body parts, aircraft,
eyeglasses, etc.