19.5 Rocks and Minerals

The world formed from Stardust
We formed from the world
We all came from Rocks
So now Mrs Stanford is calling us
Nuclear waste and Rock-heads
the three major types of
rocks and how they form
Discuss physical and chemical
properties of each major type of
Describe the rock cycle
Explain how to find relative rock
ages and absolute rock ages
 Diamond,
the hardest mineral on
earth, is composed of Carbon. The
same material needed for life as we
know it.
 Most of the earth’s crust is made of
some form of quartz
 Diamonds, Rubies, Quartz, Garnets,
and most of the precious gems we
are familiar with come in many colors
burns white and very
hot (don’t believe me, burn an
old VW Bug engine in a bonfire)
Copper burns green (copper is
also toxic, many gem cutters
don’t work with Malachite, which
is a semi-precious gemstone
containing copper)
natural, inorganic solid with a
definite chemical composition and a
characteristic internal structure
 Ex. Quartz, is silicon dioxide, SiO2
Think of Triangular Pyramids being
put together a specific way, over
and over and over
 Granite
is a rock composed of
different minerals
 Coal
is decomposed plant matter
 Appearance
and Characteristics
reflect mineral composition (what is it)
and the way it was formed
are three major types of rocks –
 There
 Remember
the difference between
Magma and Lava
Magma is underground
Lava is on the surface
 Granite
from magma
 Granite cools
 Granite is course
 You can see
different grains
 Obsidian
from lava
 Cools quickly on
the surface
 Obsidian is
smooth like glass
 Obsidian you
can’t see grains
Granite is an
Igneous Rock
 Rocks
are not permanent
structures, they break down
by a process called
 Weathering
 Weathering changes the
physical form or chemical
composition of rock minerals
exposed at earth’s surface
 Weathering can be from wind,
rain, acids…
Making new rock from old weathered rock
 Rock formed from compressed or cemented
deposits of Sediment
 Sediment is weathered rock, carried away by
wind or water and deposited in an new
 Sediments can be deposited by rivers, wind
(sand dunes), glaciers, oceans…
Sedimentary rock often
includes the bodies or
remains of animals and
 Dinosaur National Monument, in North-West
corner of Colorado is a large sedimentary rock
formation that has been exposed by humans to
uncover the remains of many dinosaurs
Pressure – rocks and water above can
squeeze sediments into sedimentary rock
 “Glue” – rocks dissolve and enter pores and
resolidify gluing the sediments together
Conglomerate – made of
pebbles and large visible rocks
cemented together with a
brown material of mostly quartz
 Sandstone
 Mudstone, if flaky called Shale
 Limestone – made of fossils of
organisms that lived in water
 Forms
 Limestone dissolves
in water and leaves a
cavity in the ground
 Some minerals that
are already in the
water deposit in the
cave leaving
found in
 Rocks
that started as
Igneous or Sedimentary
can be changed by
“squeezing”, “heating” or sometimes
a chemical process
 Usually both heat and pressure are
involved in metamorphosing a rock
Heat and
pressure turn
limestone into
Marble will often
have bands of
color and swirls
Shale (remember that’s flaky mudstone) turns
into slate when heated and compressed
 Shale and slate are often rock types where oil
and natural gas can be found
 Geologists searching for gas and crude oil
look for evidence of these rocks
Can be hard to tell
 We can find relative
age using
 “Law of Superposition”
Older rocks are on
the bottom,
 Examples Grand
Canyon, Layers of
rocks seen in Grand
Junction Area…
 Fossils in rocks
lower in a rock face
are older than fossils
in rocks above them
Radioactive elements will “decay”
- they break down to other elements or forms
 Carbon, Argon, Rubidium, Strontium, Uranium
and Lead are all used for Radioactive Dating
 Determines absolute age of rock
Rocks in Minnesota are 3.2 billion years old
 Rocks in Greenland are 4.2 billion years old

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