Download Organic Rocks - Ring of Fire Science

Organic Rocks
Lesson 6
A
ll organic rocks are formed by living organisms. Plants and animals produce limestone
from calcium carbonate, which is the mineral calcite. They create shells by extracting the
calcium carbonate from seawater. Plant material creates sedimentary layers when it falls
into swamps and bogs. The plant material transforms into coal, a rock that burns. In this lesson,
you will be learning about these rocks and how they form.
Here are some interesting facts about
organic limestone.
♦ Unlike most rocks, limestone is
created principally from one
mineral calcite (KAL-site). Calcite
looks a lot like quartz. It is much
softer than quartz and reacts with an
acid.
♦ Organic limestone always forms in
water.
♦ Plankton floating on the surface of
the ocean creates microscopic shells
of calcite.
♦ Most organic limestone forms in a
shallow marine environment.
Limestone comes in a variety of colors. It
can be gray, white, black, or pink. Take out
the limestone in your kit and look it over
carefully. Notice its color and how it feels
when you rub your fingers over it.
NOAA
Coral
Chalk is a fine-grained limestone made from the shells of foraminifera (fo-ram-eye-NIF-er-ah),
one-celled animals. These minute one-celled animals create test, shells, of calcium carbonate,
which fall to the ocean floor when they die. Blackboard chalk is the compacted shells of these
tiny sea creatures mixed with clay. Look over the sample of white chalk in your kit. Rub the
chalk with your fingers. Does it feel gritty or smooth? Look at it with your keychain microscope.
Diatoms (DI-ah-toms), minute sea creatures similar to foraminifera, extract silica (quartz) from
ocean water to build their tiny shells. When these small animals die their shells drift down
forming layers of silica. The silica layers compact to form a soft light-colored rock called
diatomite. Diatomaceous earth is white and crumbly. Diatomaceous earth (DE) is an inexpensive
material used for water treatment.
Coal seams, exposed in road cut on Glenn Highway, Alaska
Plants that die and fall to the ground in swamps and bogs form sedimentary layers of plant
material. The plant material does not decompose because it is underwater. The rock that forms
from these plants is coal. Take out the piece of coal in your kit. Look at it carefully with your
hand lens. Notice how black your piece of coal is. All coal must contain at least 50% carbon.
Coal ranking depends on the amount of carbon in the rock. The greater the concentration of
carbon in coal the higher it is ranked.
Peat is not coal but compressed plant material used as fuel in some countries. Brown coal forms
when peat is compressed creating a low-grade coal. Bituminous coal contains more carbon than
brown coal and industry uses it to make electricity.
Lesson Summary
♦
Sea creatures extract calcium carbonate, a chemical, from ocean water and use it to create
their shells.
♦ Plants that die and fall to the ground in swamps and bogs form sedimentary layers of
plant material that can turn into coal.
♦ Diatoms, minute sea creatures similar to foraminifera, extract silica from ocean water to
build their shells.
Name __________________________
Date ___________________________
Quiz 6
Organic Rocks
Fill in the blanks using words from the Word Bank
1. Sea creatures extract calcium carbonate, calcite, from ocean water and use it to create their
.
2. Peat is not coal but compressed plant material used as
countries.
3.
in some
, is a fine-grained limestone made from the shells of
foraminifera, one-celled animals.
4. Bituminous coal contains more
uses it to make electricity.
than brown coal and industry
5. Diatoms, minute sea creatures similar to foraminifera, extract
from ocean water to build their shells.
6. Limestone forms principally from one mineral
most rocks that contain more than one mineral.
7. Coal’s ranking depends on the
, unlike
of carbon in the rock.
8. The greater the concentration of carbon in
ranked.
9. Brown coal forms when
the higher it is
compresses into a low-grade coal.
10. Plants that die and fall to the ground in swamps and bogs form sedimentary layers of
material.
Word Bank
chalk
coal
amount
shells
silica
plant
carbon
calcite
fuel
peat
Testing For Calcite
Activity 6
Introduction
Pure limestone is made of one mineral calcite. Sea animals extract calcite from ocean water and
use it to build homes that protect them from predators. The outside covering of chicken eggs is
made of calcite also. Scientists use acid to test for calcite in rocks because when dissolves
calcite. The process releases carbon dioxide, a gas, into the air. In this activity you will use
vinegar, which is an acid, to test for calcite.
Materials
♦
♦
♦
Shells or egg shells
Vinegar (any kind will do)
Small container
Directions
1. Collect some eggshells that have
been used in cooking or use a
broken seashell.
2. Place the eggshells in a small
container.
3. Pour a small amount of vinegar
onto the shells.
4. Observe what is happening to the seashells for several minutes. Have any bubbles appear
on the shell? If you observe bubbles on the shells this is carbon dioxide forming as the
vinegar reacts to the calcite in the shells.
5. Completely cover the shells with vinegar. Watch to see if the amount of bubbles
increases or decreases.
6. Observe what happens to the shells during the next 30 minutes.
7. Leave the shells in the vinegar overnight. What happened to the shells?
Recording your experiment
1. Write the title of the activity beneath your lesson summary.
2. List the actual materials used for the experiment.
3. Write down the steps you followed to complete the experiment.
4. Write down your conclusions.
Extension
♦
♦
Test some unknown rocks to see if they might contain calcite.
Start a collection of seashells.