1. INVESTIGATING AND CLASSIFYING THE 3 ROCK TYPES

2. IGNEOUS METAMORPHIC
 GRANITE  GARNET MICA SCHIST
 GABBRO  PHYLLITE
 OBSIDIAN  SOAPSTONE (SCHIST)
 PUMICE  MARBLE
 SCORIA  AMPHIBOLITE

3. SEDIMENTARY
 SANDSTONE
 OIL SHALE
 LIMESTONE
 FOSSIL LIMESTONE
 ROCK GYPSUM

4.  Igneous rocks form from
cooled molten material
 If magma crystallizes
underground, then the
rock is INTRUSIVE
 If lava cools above
ground, then the rock is
EXTRUSIVE
 At one point in Earth’s
history, all rock was
igneous

5.  GRANITE (intrusive)
 Large, interlocking crystals
 Forms from slow
crystallization of magma
 Composition:
 Quartz
 Feldspar
 Mica
 “Dimension Stone”
 Hard (resists scratching)
 Strong (bears much weight)
 Inert (resists weathering)
 Polishes brilliantly

6.  GABBRO (intrusive)
 Course grained
 Usually dark green
 “Black Granite”
 Composition
 Plagioclase
 Augite
 Very little quartz
 Uses
 Cemetery markers
 Counter tops
 Floor tiles

7.  OBSIDIAN (extrusive)
 Molten lava cools
quickly (extrusive)
 “Volcanic glass”
 Composition
 No minerals
 Most is at least a few
million years old
 Not found east of the
Mississippi
 Used as a cutting tool

8.  PUMICE (extrusive)
 Lava cools during
flight, forming pores
 During an explosive
volcanic eruption, may
rain down from the sky
 High silica content
 Uses:
 Abrasives for cleaners
 Scouring agents
 Insulation

9.  SCORIA (extrusive)
 Often forms as the top
of a lava flow cools
 Many of the same uses
as pumice
 Porous, light
 Higher basalt content
than pumice, giving it a
red to black color

10.  These form from
existing rocks that
are chemically
changed by high heat
and/or pressure
 Parent rocks can be
igneous, metamorph
ic, or sedimentary

11.  SCHIST
 Intermediate; between
phyllite and gneiss
 Foliated (low-grade)
 Contains lots of
mica, which allows it to
split into pieces
 Garnet mica schist
contains small garnet
crystals (dark red)

12.  PHYLLITE
 Well defined foliation
 Made of mostly fine-
grained mica
 Intermediate; between
slate and schist
 Formed from morphed
shales or mudstones
 Sedimentary layers have
been preserved
 Orange tint indicates
presence of iron

13.  TALC SCHIST
(SOAPSTONE)
 Extremely soft
 Soapy or greasy texture
 Talc
 Softest mineral on Earth
 Used in baby powder
 Some areas of the San
Andreas Fault contain
soapstone
 Limits severity and
frequency of earthquakes
 Alabaster, serpentine

14.  MARBLE
 Recrystallized limestone
or dolemite, hence the
white color
 Composed entirely of one
mineral: calcite
 Often found interbedded
with
schists, phyllites, gneisses,
and granulites
 If the marble has other
colors, it is because of
impurities in the original
limestone deposit
 Uses:
 Buildings, monuments, tab
letops

15.  AMPHIBOLITE
 Parent rocks:
 Basalt, gabbro, dolemite
(sedimentary)
 Medium to coarse-
grained crystals
 Hornblende and
plagioclaste (ex.)

16.  Sedimentary rocks form
from pieces and parts of
older
rocks, plants, skeletons, s
hells, or other debris
 Most of the rock in our
area is sedimentary, like
sandstone and slate
 Sedimentary rocks are
the only rocks that we
find fossils in

17.  LIMESTONE
 Composed primarily of
CaCO3 (calcium
carbonate), or calcite
 Forms underwater, from
shells and skeletons of
dead sea creatures
 Fossil rich
 Common in PA
 Limestone blocks were
used to construct the
Great Pyramid of Egypt

18.  SANDSTONE
 Clastic rock made up of
fine grains of sand
“glued” together by
minerals (usually
quartz)
 Common to
beaches, floodplains, de
ltas, and deserts
 Siltstone, mudstone
 A red tint indicates the
presence of clay

19.  OIL SHALE
 Shale is extremely
common in
riverbeds, under, and
around lakes
 Forms from the
compaction of silt and
clay sized particles
 Black shales contain
organic materials that
produce oil, natural
gas, and coal

20.  ROCK GYPSUM
 Gypsum is a common
mineral that is used in
drywall, plaster, and
concrete
 Sulfate mineral (SO4)
 Forms in caves
 Satin spar gypsum and
alabaster are used in
decorative pieces

21. ROCK ON!
And thank you geology.com for all your
useful info and pictures!