Download 2. Minerals

6. Minerals and Rocks
6.1 Minerals are all around us
6.2 Rocks form in different ways
6.3 Natural processes break down rocks
6.4 Geologic maps show Earth’s surface
features
6.1 Minerals are all around us
• Before, you learned:
– Earth is made of layers
– Earth’s outermost rocky layer is the crust
• Now, you will learn:
– About the characteristics of minerals
– How minerals are classified into groups
– Which mineral group in most common
Warm-up Questions
• Latitude is a distance in degrees
________ or _________ of the _________
• (T/F): Relief maps use contour lines to
show features
• Geographic information systems display
data in _____ to build maps
Minerals and rocks are part of
daily life
• Wires carrying eletric current are made of
copper – a mineral!
• Table salt (halite) – a mineral!
• The Earth’s crust is made of rocks –
almost all rocks are made of minerals!
Minerals
• Minerals are not the same as rocks
• A rock has only two of the characteristics
– Solid and forms in nature
– A rock usually has two or more types of minerals
• Minerals are always made up of the same materials in
the same proportions
– Quartz crystal has 2 Oxygen atoms for every silicon
atom
Minerals
• A mineral is (generally) an inorganic, naturally occurring,
organized crystalline structure composed of a single
chemical compound or element.
• A rock is (generally) a natural solid composed of multiple
crystals of one or more minerals
– Although many rocks contain visible crystals of individual
minerals, a rock itself does not have an overall crystalline
structure.
Minerals have four characteristics
" A naturally occurring,
inorganic material of
constant chemical
composition and a definite
crystalline structure."
1. Form in nature
2. Are solids
3. Have a definite chemical makeup
4. Have a crystal structure
Examples: copper in the wires that carry
electricity, table salt (halite)
Is water a mineral? Is ice?
Can minerals be found in rocks?
Minerals – 1. Formed in Nature
• Can be formed by processes that do not necessarily
involve living organisms
• A few minerals can be produced by organisms as part of
shells or bones
• Haline forms when water evaporates in a hot shallow
part of the ocean
• Granite forms when molten
rock cools
Minerals – 2. Solids
• Definite volume and a rigid shape
– Volume: amount of space an object takes up
Minerals – 3. Definite Chemical
Makeup
• Specific combination of atoms of certain
elements
– Element: a substance that contains only one
type of atom
– Atom is the smallest particle an element can
be divided into
– Most minerals contains more than one
element – compounds – elements in specific
proportions
Halite – NaCl
Copper - Cu
Minerals – 4. Have a Crystal
Structure
• Crystal: solid in which
the atoms are
arranged in an
orderly, repeating 3-D
pattern
• Two minerals can
have the same
chemical composition
but different crystal
structures
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• Diamond and graphite are
both made of Carbon
• The individual atoms have
the same properties, but are
in different arrangement
giving the substance very
different properties – different
crystal structure
Minerals are grouped according to
composition
• Grouped on the basis of chemical makeups
• Most common group is silicates
– Contain oxygen silicon – most common in Earth’s
crust – joined together
• Rock-forming minerals
– The 30 minerals that make up most of the crust
– Silicates make up 90% of the rocks in the crust
• Quartz, feldspare, and mica
– 2nd most common: Carbonates (carbon and
oxygen) - calcite
Rocks are made of minerals
• Minerals
– must have the four previously mentioned characteristics
– Always made of the same elements in the same proportions,
have an orderly crystal structure
• A rock only has two of the four:
– It is a solid and forms naturally
– Rocks are usually made of two or more minerals
– The proportion of different minerals in a certain type of rock may
vary
– The minerals in a rock can be all jumbled together
– Only a few types of rocks are made of only one type of mineral
• Ex: limestone (calcite)
– A few contain no minerals at all
• Ex: obsidian (made of natural glass – no crystal structure)
• Ex: Coal (remains of ancient plants)
Math in Science
• Each mineral makes up a certain proportion, or fraction,
of a granite sample
– You can compare mineral amounts by expressing
each mineral’s fraction as a percentage
• To change a fraction to a percentage, you must find an
equivalent fraction with 100 as the denominator
– 1/5 to percent?
• First, divide 100 by the denominator 5 = 20
• Then multiply the numerator and denominator by
20 = 20/100 = 20%
Minerals in a Granite Sample
Mineral
Fraction of
granite sample
quartz
1/4
feldspar
13/20
mica
3/50
Dark minerals
1/25
Percentage of
granite