IV. 3 Rock Categories
A. Igneous
1. Origin
Intrusive
Extrusive
Igneous rock that formed
when magma hardened
beneath Earth’s surface
Ex. Granite
Igneous rock formed from lava
that erupted onto Earth’s
surface
Ex. Basalt
2. Texture
a.
b.
c.
d.
Depends on size/shape of mineral crystal
Intrusive – larger crystals (coarse-grained)
Extrusive – smaller (if any) crystals (fine-grained)
Porphyritic Texture (combo of two)
IV. 3 Rock Categories
3. Mineral Composition
a. Silica (Material that is a combination of Oxygen and
Silicon)
i.
ii.
Low-Silica Lava = dark-colored rocks (like Basalt)
High-Silica Magma = light-colored rocks (like Granite)
HOMEWORK
• Read Chapter 3, Section 2 (pages 78-81)
• Index Cards for bold vocabulary words found
in Section 2
• Section 2 Review, # 2, 4, 5
Granite in Architecture
This is a sample of granite architecture found
in Aberdeen, Scotland. Granite is a very
durable, strong rock used in buildings, statues,
monuments, and structures throughout the
world.
Granite Slabs and Stones Used in the Kitchen
Granite is commonly used
in the kitchen not only for
its beautiful colors and
patterns but also because
it can withstand extreme
temperatures. You can
cook food on granite to
enhance the flavor of
certain meals.
Primp and Perm with Pumice
An igneous-volcanic rock, pumice is a porous, brittle
variety of rhyolite and is light
enough to float. It is formed when magma of granite
composition erupts at the earth’s surface
or intrudes the crust at shallow depths. It is used as
an abrasive material in hand soaps,
emery boards, etc.
Gabbro Quarries Used to make Paving Stones
Gabbro is a durable igneous rock that is
commonly found in paving aggregates. Roads
and architectural features can be made from
Gabbro.
Materials for Hot Rock Therapy
This type of therapy requires stones that
preserve warmth. Basalt stones are particularly
common and can be heated as high as 140
degrees.
Basalt Stones For Massages
Basalt stones are very popular products for use
in massage. Formed from volcanic rock known
for its smooth texture, basalt rocks are
particularly amenable to high temperatures.
When heated, these stones retain their
warmth for long periods of time and are
therefore ideal for stone therapy.
Igneous Rocks Used for Cooking
Several older Char-Broil gas grill models
incorporated lava rocks near the grill burners
to help distribute heat from gas-fed flames
evenly throughout the grilling chamber. Lava
rocks retain heat, making grilling more
efficient. The rocks are heated by the gas flame
and cook like charcoal.
Lava rock heats quickly and disperses the heat
to the interior of the grill. Lava is porous and
allows grease to accumulate, lessening its
efficiency and increasing flare-ups. Replace
lava rock yearly or turn over to expose a fresh
surface.