Download Sedimentary Rocks

IDENTIFYING ROCKS LAB
IMPORTANT: PLEASE MAKE SURE TO KEEP THE ROCK SAMPLES IN
THEIR CORRECT CUP. IF YOU FORGET WHICH ROCK BELONGS IN A
NUMBERED CUP USE MRS. ELAMPARO’S ROCK SAMPLE KEY. THANKS!
Objective: How can a scientist identify whether a rock is igneous, sedimentary and
metamorphic?
Background: A rock is a hard substance composed of one or more minerals. Rocks are
placed into three groups according to how they form: igneous, sedimentary and
metamorphic. Igneous rocks are formed from fluid magma within the Earth.
Sedimentary rocks are formed from particles that have been carried along and deposited
by wind and water. Metamorphic rocks are formed when chemical reactions, tremendous
heat, and/or great pressure change existing rocks into new kinds of rocks. A continuous
change of rock from one kind to another is called the rock cycle.
Procedure:
1) Carefully observe your rock samples.
2) Draw a data table like the one below on your paper.
Rock #
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Description
Classification
Rock Name
3) Record a brief description of the rock sample in your data table.
4) Compare your group’s rock samples to the pictured rock samples on pages 418-427 in
the EARTH SCIENCE textbook.
5) Using the above pages in the text and the supplemental “Rock Info” sheet determine
the classification of each rock as igneous, sedimentary or metamorphic.
6) Record the rock’s classification in your data table.
7) Lastly, determine the rock sample’s name in your data table by using your textbook
and “Rock Info” sheet.
Conclusions:
1) What is a rock?
2) Explain the rock cycle.
3) What is the most outstanding feature of pumice? Why does it have this feature?
4) What is the origin of obsidian? How can you tell by looking at it?
5) What are the dark spots in granite and diorite? What are the light spots?
6) What is a conglomerate made of? Why might a big business be called a
conglomerate?
7) What is sandstone made from? What is shale made from?
8) Compare diorite and gneiss. What does it look like happened to gneiss when it was
made from diorite?
9) Compare shale and slate. Which one is harder?
10) Of all the rock samples, which is a natural glass, often used by Native Americans for
arrowheads because the broken glass edges were sharp?
11) Write a conclusion statement about the objective to this lab activity.
Igneous Rocks
A) Granite: A common igneous rock composed of quartz, feldspar and biotite mica.
This rock is used as a building stone.
B) Pumice: Solidified from lava in which a gas cavity forms within solid material. It
will float on water.
C) Diorite: An intrusive igneous rock. With little or no quartz its components are
feldspar and usually hornblende or biotite mica.
D) Obsidian: An extrusive igneous rock made when magma is suddenly ejected from a
volcano. Some of it cools rapidly that there is no time for crystallization of the
mineral ingredients. It solidifies essentially as a glass with little organization of
mineral structures.
Sedimentary Rocks
A) Sandstone: Formed from quartz sand packed by pressure of overlying layers of
rocks. It is used in building stone and road construction. The tan, brownish or
reddish color in the sandstone is caused by iron oxide.
B) Shale: Formed by clay mud packed hard by weight of overlying sediments. It is
made into rock by compaction and squeezing out or evaporation of its water content.
C) Conglomerate: A sedimentary rock consisting of rounded fragments of other rocks
or minerals cemented together. The fragments have become rounded by friction in
moving water.
Metamorphic Rocks
A) Gneiss: Made from igneous or sedimentary rocks. Quartz, feldspar and biotite are
usually present. Gneiss is usually coarse-grained with more or less parallel stripes of
dark minerals such as mica or hornblende alternating with lighter colored stripes of
quartz and/or feldspar. Much gneiss is derived from rocks such as diorite and granite.
B) Schist: Formed from gravel or sandstone and composed of biotite, muscovite, quartz
and feldspar.
C) Slate: Produced from shale metamorphosed by pressure. Pressure causes the
minerals to arrange themselves in planes with their flat sides perpendicular to the
direction of pressure. Slate, therefore, will split along the planes. It occurs in a
variety of colors such as gray, black, red or green.