Name:_________________________________ Class:______________________ Date:________________
Earth Science- Ms. Gill
Rocks & Minerals
Rock Identification Station Lab
Introduction: All rocks are classified based on how they form. Sedimentary rocks are formed from accumulated
sediments, mostly deposited in calm water. Metamorphic rocks are those that have formed from other rocks as a
result of the action of heat, pressure, and/or chemical action. Igneous rock is formed when molten magma or lava
solidifies and the type depends on the mineral composition and the rate at which the magma cools. In this lava you
will observe many different rocks of each type and discover how they were formed.
Station #1: Sedimentary Rocks
Background Information: A SEDIMENTARY ROCK is one that has been formed by the “cementation” of sediments
through “compaction.” There are three major categories of sedimentary rocks:
1. Clastic (Fragmental) Sedimentary Rocks: those that are made of rock and mineral fragments. A Fragmental
Sedimentary rock is one that is made of sediments, or broken down particles of other rocks, that are held
together by a hard crystalline cement. In clastic sedimentary rocks there are only 3 major minerals likely in the
rock, quartz, feldspar, and clay particles. Fragmental rocks are classified based on differences in grain sizes or
differences in texture.
2. Bioclastic (Organic) Sedimentary Rocks: those that are made from the accumulation of organic material such as
plant and animal remains. One example is Fossil Limestone, which is made mostly of fossils, shells, and shell
fragments. Another example is Bituminous Coal which is made of organic remains of plant and animal matter and
usually appears black.
3. Crystalline (Chemical) Sedimentary Rocks: those that are made from chemical processes such as precipitation
and evaporation. These are rocks that are formed by sediments that are chemically or organically formed. The
chemical processes that are responsible for the formation of these sediments are evaporation and precipitation.
These are rocks that tend to be composed of only one mineral and are thus said to be “Monominerallic.” Since these
rocks tend to be Monominerallic, the identification of these rocks are based on the mineral that makes up the rock.
There are 4 major non-clastic rocks of interest for this lab:
1. Chemical Limestone: composition = calcite (fizzes in HCl) No fossils visible. Formed as a precipitate in tropical
ocean waters. Water becomes supersaturated with calcite so the calcite precipitates out of solution.
2. Rock Salt: composition = halite (evaporite). Will taste like salt. Forms when salt water evaporates.
3. Rock Gypsum: composition = gypsum (evaporite). Can be scratched by a fingernail.
4. Dolostone: composition = dolomite. Fizzes in HCL only when powdered.
Vocabulary:
Clastic:________________________________________________________________________________
Lithification:____________________________________________________________________________
Cementation:____________________________________________________________________________
Compaction:_____________________________________________________________________________
Precipitates:____________________________________________________________________________
Fossiliferous:____________________________________________________________________________
Organic:_______________________________________________________________________________
Sedimentary Rock Data
Sample
Texture
Composition
Method of Lithification
Rock Name
#
-Clastic
If Clastic or Bioclastic:
(formation)
-Use your ESRT
(fragmental)
-describe fragment
-Cemented & Compacted rock
page 7.
-Crystalline
shape
fragments
(Chemical)
-describe grain size
-Cemented shell fragments
-Bioclastic (from
OR If Crystalline
-Compacted plant remains
Life)
-give mineral
-Crystals from chemical
composition
precipitates and evaporites
1
2
3
6
7
8
10
15
Questions:
1) What are the maximum and minimum dimensions (size range) for the following particle sizes:
a) cobble:______________________ b) Pebble:_______________________ c) sand:___________________
2) How can you distinguish a clastic sedimentary rock from a chemically formed sedimentary rock?
______________________________________________________________________________________
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3) Describe the sequence of events in the formation of an evaporite:
______________________________________________________________________________________
______________________________________________________________________________________
4) Describe the sequence of events in the lithification of a sandstone:
______________________________________________________________________________________
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5) Explain why sedimentary rocks are found as a thin veneer covering large areas of the continental igneous rocks?
______________________________________________________________________________________
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6) How are fossils formed in sedimentary rocks?
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Station #2: Metamorphic Rocks
Background: Metamorphic Rocks are rocks that have been changed by the action of heat, pressure and fluids.
These forces can either cause minerals in the original rock (called the host rock) to rearrange and form new
minerals, or will cause a distortion of existing minerals. All types of rocks---igneous, metamorphic and sedimentary--are subject to metamorphism.
Metamorphic Rocks can form in two major environments:
1. Regional Metamorphism: this is large scale metamorphism that can occur over 100’s to 1000’s of miles. This
type of metamorphism occurs during the processes associated with mountain building. Mountains are formed when
two plates collide. This type of collision produces a tremendous amount of heat and pressure. This heat and
pressure causes distortion and the rearrangement of minerals in a rock. As a result, regionally metamorphosed
rocks tend to show intense folding, banding, or foliation (can be split into layers).
2. Contact Metamorphism: this is small scale metamorphism that occurs over only several hundred feet. This type
of metamorphism is caused by a magma intrusion where pressures are low and temperatures are high. The resulting
changes in the rock are not as drastic as in regional metamorphism. FOLIATION DOES NOT OCCUR IN THESE
TYPES OF ROCKS.
Texture in metamorphic rocks is defined as the degree of foliation in a rock. The texture can either be:
a) foliated—shows mineral alignment or banding
 slaty: flat breakage or fracture. No grains are visible.
 schistose: cleavage similar to the mineral mica, shiny due to flattened crystals.
 gneissic: no cleavage present. Strong banding; alternating light and dark bands.
b) non-foliated—no banding or layering present
Vocabulary:
Recrystalization:_________________________________________________________________________
foliation:_______________________________________________________________________________
Schistose foliation:_______________________________________________________________________
Banding:_______________________________________________________________________________
Mineral Alignment:_______________________________________________________________________
Parent Rock:____________________________________________________________________________
Metamorphic Rock Data:
Sample
Texture
Type of Metamorphism
Probable
Rock Name
#
-Nonfoliated
-Regional
Original
-Use your ESRT
-Foliated (if foliated give type:
-Contact
Rock
page 7.
Banding or Mineral Alignment)
-Either
1
3
6
9
12
Questions:
1. What is the difference between contact and regional metamorphism?
______________________________________________________________________________________
______________________________________________________________________________________
2. Why are metamorphic rocks formed by contact metamorphism usually not as dense as those formed by regional?
______________________________________________________________________________________
______________________________________________________________________________________
3. How could you differentiate between white marble and white quartzite?
______________________________________________________________________________________
______________________________________________________________________________________
4. Why do you seldom find fossils in metamorphic rocks?
______________________________________________________________________________________
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5. Why do minerals in metamorphic rocks often rearrange into bands?
______________________________________________________________________________________
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6. Why is quartzite very hard and more resistant than its parent rock?
______________________________________________________________________________________
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7. How do you classify metamorphic rocks?
______________________________________________________________________________________
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Station #3: Igneous Rocks
Background Information: Igneous rocks are rocks that are formed from molten (liquid) rock. Igneous rocks can
be categorized based on where they form and the composition of the magma or lava it forms from. Both of these
factors control the appearance of igneous rocks. Understanding the conditions of formation is essential for
identification.
Igneous rocks can form in two ways:
1) Beneath the earth’s surface, this is called a plutonic environment and this produces intrusive igneous rocks.
This results in slow cooling of the magma and therefore crystal size is coarse, meaning large.
2) Above the earth’s surface, this is called a volcanic environment and this produces extrusive igneous rocks.
This results in fast cooling of the lava and therefore crystal size is fine, meaning small. Sometimes the rock cools
so quickly that no crystals form resulting in a glassy texture.
A porphyritic texture is when an igneous rock exhibits two different grain sizes related to two different rates of
cooling among minerals present. Here texture is both coarse and fine, this is common in rhyolites and andesites.
The composition of magma and lava can vary. This results in 3 major divisions based on color and composition:
1) Light colored felsic composition. These mineral have a low density. Major colors include pink to white.
Predominant minerals are K-feldspar and quartz with minor amounts of hornblende, plagioclase, and biotite
2) Intermediate colored—intermediate composition. Major colors include 50% dark, 50% light.
Predominant minerals are Plagioclase, biotite, and hornblende.
3) Dark colored mafic composition. These mineral have a high density. Major colors include gray, green, and black
Predominant minerals are plagioclase, pyroxene, olivine, and hornblende.
Vocabulary:
Igneous:_______________________________________________________________________________
intrusive:____________________________________________________________________________
extrusive:____________________________________________________________________________
felsic:_____________________________________________________________________________
mafic:____________________________________________________________________________
lava:____________________________________________________________________________
magma:_______________________________________________________________________________
texture:______________________________________________________________________________
pultonic:_______________________________________________________________________________
volcanic:_______________________________________________________________________________
Igneous Rock Data:
Sample
Color &
Texture;
Method of
Mineral Present
Rock Name
#
Composition:
-Glassy
formation:
Use colors to
-Use your ESRT
-Light and Felsic
-Vesicular
-Intrusive
identify minerals
page 6
-Dark and Mafic
-Random Intergrown
-Extrusive
Crystal (include grain size)
1
5
8
11
12
14
15
No #
Questions:
1.
How is the size of the mineral grains affected by the rate at which molten rock is cooled?
______________________________________________________________________________________
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2.
How can you determine if an igneous rock is intrusive or extrusive?
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3.
Compare and contrast Granite and Basalt?
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4. In general how does the density & mineral composition of a light colored igneous rock differ from that of a dark
colored igneous rock?
______________________________________________________________________________________
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5. What is the main difference between lava and magma?
______________________________________________________________________________________
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6. Describe a porphyritic texture:
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7. What are the two major ways that igneous rocks vary from one another?
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8. On what basis are igneous rocks classified
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