Transcript Rocks Minerals PPT (3).

What is a rock?
A rock is a naturally occurring solid substance that is
normally made of minerals.
Some rocks are made of only one mineral. Others are
made of several minerals combined.
By figuring out what minerals are in a rock and
understanding how they are formed geologist place
rocks into one of three groups:
Igneous
metamorphic and sedimentary .
What is a mineral?
Minerals are the building blocks of rocks.
Scientists have discovered over 3,000 types of minerals!
A mineral is a natural, nonliving substance.
Properties of minerals
Color: Color alone, cannot identify minerals. Many
minerals have the same color.
Quartz can be many different colors!
Hardness: refers to a minerals ability to scratch
another mineral or be scratched. The MOHS’ Scale
shows the hardness of some common minerals. Each
mineral has a number one - ten. Ten is the hardest
kind.
Luster: refers to the way light bounces off the surface
of a mineral. Some have a metallic, or shiny luster.
Minerals with no shine at all have a dull luster.
Streak: If you scratch a mineral along a white tile,
it leaves behind a powder. A minerals streak is the
color of that powder. The streak may be different from
the color of a mineral’s surface!
Properties of minerals
mineral
color
mica
feldspar hematite
pyrite
white, green, white, pink,
gold or
silver, or
gray, or
gray or brown
brassy yellow
brown
smoky black
luster
pearly
dull or glassy
metallic or
dull
streak
white
white
red
green-black
hardness
2 - 2.5
6-6.5
6-6.5
5-6
metallic
Igneous Rocks
Below earth’s surface are areas of melted rock
called magma. When magma cools and hardens,
igneous rocks form.
neous rocks can also form from lava above earth’s crust.
The texture of an igneous rock depends on how fast the
magma cools to form the rock.
The slower it takes to cool the more mineral grains will form. If it cools
quickly, the rock will have a smoother, glassy texture.
obsidian
granite
basalt
Sedimentary
Rocks
These layers are made of tiny
pieces called sediments.
Some sediments are formed from
rocks or minerals.
Others are bits of plants, shells, or
other hard materials.
Sedimentary rocks are formed from sediments that are
pressed and cemented together.
It can take millions of years for sediments to become rocks!
metamorphic
Rocks
When rocks are under extreme heat or
pressure (like under earth’s surface!) their
physical appearance can change.
A metamorphic rock is a rock that is formed from other
rocks by extreme heat and pressure.
granite
gneiss
The Rock Cycle