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Sedimentary
Igneous
Metamorphic
What are minerals?
• Minerals are naturally occurring, nonliving
substances found in Earth.
• They have a chemical formula, and a
definite internal structure.
Characteristics of Minerals
• There are 3500 known minerals in Earth’s crust.
• No more than 20 of these are commonly found in rocks.
• Rocks are therefore made up of combinations of minerals
cemented together under extreme heat and pressure.
Rock forming minerals
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Feldspar
Pyroxene
Mica
Olivine
Dolomite
Quartz
Amphibole
Clay
Calcite
Rock characteristics
• Porous, granular, or smooth
• Soft or hard
• Densities
The appearance reflects it’s mineral composition
and how it was formed!
Identifying Minerals by physical
characteristics
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Color
Luster
Transparency
Cleavage
Fracture
Streak
Hardness
Igneous Rocks
• Igneous – from fire
• Magma – molten material inside the earth.
• Lava – molten material which flows on or
above the earth’s surface.
Igneous Rocks
• Igneous rock forms when molten rock cools
and solidifies.
• Intrusive: cools within the earth.
• Extrusive: cools on or above the earth’s
surface.
• Made of various mineral crystals.
• The more quickly the rock cools, the less
the crystals grow.
Examples of Igneous Rocks
Granite
Basalt
Course Grained
Cooling is slow; thousands to millions of years
Cools below the ground - intrusive
Minerals can be seen with the naked eye
Fine Grained
This rock has cooled “quickly” days to weeks
Minerals do not have time to grow
Grains are very small – above ground - extrusive
Example: rhyolite
Obsidian
If cooling is extremely quick (hours to days)then no minerals form.
Example: obsidian
Sedimentary Rocks
• Rocks formed from compressed and
cemented deposits of sediment.
• Sedimentary rocks are like recycled rocks.
• Contain older rocks and sometimes, fossils.
Formation of Sedimentary Rocks
• Weathering causes rocks to break down;
waves, wind, rain
• Pieces of rock accumulate forming
sedimentary rock
Formation: 2 ways
• Sediment accumulates- weight from layers
above compress the sediment forming rock
• Minerals dissolved in water seep between
bits of rock and “glue” them together
Sedimentary Classified as 3 types
1. Detrital – from the Latin word detritus
meaning to wear away.
Rocks made from broken rock material.
2. Chemical – when minerals are
precipitated from a solution or left
behind from evaporation.
3. Organic – formed from the remains of
once-living things.
For thousands, even
millions of years, little
pieces of our earth have
been eroded--broken down
and worn away
by wind and water. These
little bits of our earth are
washed downstream where
they settle to the bottom of
the rivers, lakes, and
oceans. Layer after layer of
eroded earth is deposited on
top of each. These layers are
pressed down more and
more through time, until the
bottom layers slowly turn
into rock.
Examples of Sedimentary Rock
Sandstone- made up of small
grains of quartz and feldspar
that form in layers
Limestone- made from the
mineral calcite which came
from the beds of evaporated
seas and lakes and from sea
animal shells
Examples of Sedimentary Rock
Shale- made of compacted clay
Conglomerate- made of large sediments and
small particles such as sand and pebbles,
medium to large rock fragments.
Held together by dissolved minerals
Examples of Sedimentary Rock
Gypsum
Made of sulfate mineral and formed as the result of
evaporating sea water in massive prehistoric basins.
Parent Rocks- Sedimentary
Metamorphic
• Metamorphic rock is formed from other
rocks as a result of heat, pressure, or
chemical processes.
• Parent rock (original rock) undergoes
intense heat and pressure within the Earth;
as a result, it changes mineral composition
and texture.
• Metamorphose or metamorphism – to
undergo a change.
Metamorphism
Parent rock/
minerals
Metamorphic rock
and minerals
Parent Rock
Metamorphic
• Limestone
• Marble
• Mudstone/ Shale
• Slate
2 Types of Metamorphic Rock
• Foliated Metamorphic Rocks:
mineral grains line up in parallel
bands.
• Non – Foliated: mineral grains
grow, change and are
rearranged but not in layers.
Rock Cycle
1. Magma cools and crystallizes to form igneous rock.
2. Igneous rock undergoes weathering (or breakdown) to form
sediment. The sediment is transported and deposited
somewhere (such as at the beach or in a delta, or in the deep sea).
3. The deposited sediment undergoes lithification (the processes
that turn it into a rock). These include cementation and
compaction.
4. As the sedimentary rock is buried under more and more
sediment, the heat and pressure of burial cause metamorphism
to occur. This transforms the sedimentary rock into a metamorphic
rock.
5. As the metamorphic rock is buried more deeply (or as it is
squeezed by plate tectonic pressures), temperatures and
pressures continue to rise. If the temperature becomes hot
enough, the metamorphic rock undergoes melting. The molten rock
is called magma. This completes the cycle.