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Regents Earth Science Lab
Mr. Freeman’s Classes
Sedimentary Rocks Lab
INTRODUCTION: Read the Article Below and Answer All 4 Questions.
USES OF SEDlMENTARY ROCKS
A variety of types of mineral deposits occur in sedimentary rocks and these resources are vital to our
industrial society. The processes of weathering and erosion produce rich sedimentary deposits of certain ore
minerals. For example, some elements that are dissolved by surface and ground waters are later precipitated
elsewhere in high concentrations. Most important of these are sedimentary iron deposits that form the basic raw
material for the steel industry. Other deposits result as minerals of high specific gravity (called heavy minerals)
are removed from rocks on land by surface erosion. These heavy minerals may concentrate in stream beds and off
coastal shores. Known as placer deposits, they yield valuable concentrations of materials such as diamonds, gold,
magnetite (iron), platinum, and tin. Weathering can also enrich certain ore deposits by chemical action on the
ground surface, dissolving and removing some of the associated minerals and thereby concentrating the minerals
that contain the ore.
A wide variety of sedimentary rocks is mined or quarried. Sand and gravel, sandstone, limestone, and
colomite, and clay are examples of materials vital to industry and for literally all aspects of construction
highways, buildings, dams, piers, etc. These materials are the basis for roadbed aggregate, concrete, stone blocks,
bricks, and mortar, Refinement of certain of these resources, for example silica-rich sands and purer clays, are
used to produce glass ceramic products, porcelain, tiles, fillers for paints and papers, and a host of industrial and
household products.
The chemically-precipitated sediment, rock gypsum, is used for construction and insulation materials,
plaster, as fertilizer, and as an insecticide carrier. Another chemical precipitate, rock salt, is used in the chemical
industry as well as for salting ice covered roads, as a preservative, and for human consumption.
Our important fuel sources, necessary to satisfy growing energy needs, are derived largely from
sedimentary rocks. Beds of coal have formed where plant remains once accumulated in swamps and were later
buried and compressed by sediment. Petroleum (oil) and natural gas occur in sedimentary rocks, products of tiny
marine organisms that gradually decayed and were convened into droplets of oily substances rich in the elements
of hydrogen and carbon. These hydrocarbons are oil and gas. The potentially “new” reserves of energy found in
tar sands and oil shale are also organically-derived materials in sedimentary rock. Likewise, a great majority of
the uranium deposits being mined for nuclear uses, including nuclear power plants, occur in sedimentary rocks.
1. Heavy minerals that are a result of weathering that occur in stream beds and off coasts are
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2. What 5 materials are found .in the answer to question 1: _____________________ _____________________
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3. What uses do mined sandstone, limestone, clay and gravel have? _____________________
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4. Silica-rich sands and pure clays are used in _____________________ , _____________________ ,
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OBJECTIVE: To identify sedimentary rocks and classify them according to their origin.
BACKGROUND INFORMATION: Sedimentary rocks are the products of loose material, called sediment that
has hardened into rock. Sediment consists largely of minerals, rock fragments, and organic debris that has
accumulated over thousands, even millions, of years and has gradually been converted into rock. The primary
basis for classifying sedimentary rocks into groupings is the origin of their sediments.
Clastic sedimentary rocks are composed of sediment derived from preexisting rocks. As the land surface
is altered by weathering and erosion, the particles of rocks and minerals and associated organic debris are
transported and deposited as loose material. The type of rock eventually formed depends on the size and shape of
the particles and their composition.
Chemical sedimentary rocks are derived by chemical means, primarily through precipitation of certain
elements concentrated in solution in water. These concentrated solutions then precipitate out as minerals that
accumulate in caves and on lake and ocean floors. Precipitation is sometimes accelerated by excessive
evaporation, such as the drying up of saline (salt-rich) lake waters, leaving deposits of salt-rich sediment.
Organic sedimentary rocks, as the name implies, are those rocks derived by the actions of organisms and
the accumulation of organic debris. Concentrations of plant remains also occur extensively, as well as fragments
of animal shell and skeletal material. It is common to have organic material mixed with sediments of chemical
origin, especially in those rocks containing high amounts of carbonate (C03) (fizzes in dilute acid) material.
MATERIALS NEEDED:
Rocks from Topic Set
Sedimentary Rock Classification Chart
Hand Lens
Dilute Hydrochloric Acid
PROCEDURE:
1. Examine each rock specimen closely, looking for organic debris or other evidence of organic origin. Place
these specimens into a group.
2. Among the remaining specimens, look at the particles which make up the rock. Determine whether these
particles are separate rock and mineral grains which suggest a chemical origin, or a more uniform, tightly
crystallized material indicating a chemical origin. Sort these specimens into two groups, clastic and chemical.
3. You should now have three groups of rocks sorted according to origin-clastic, chemical, or organic.
4. Have your teacher check your groups. ____________Teacher Initials
5. Next, refer to the Sedimentary Rock Classification Chart. Note that the individual rock names and the three
categories of origin have been omitted. From your investigation in the preceding 3 steps, you should be able
to fill in the names of the three categories of origins in the left column.
6. Finally, using the classification charts, identify each rock by name and complete the right hand column of the
chart.
SEDIMENTARY ROCK CLASSIFICATION CHART
SUMMING UP
1. What do the shale, siltstone, sandstone, and conglomerate have in common? What is the most significant
difference among these rocks?
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2. What is the main difference between the particles found in conglomerate and those found in breccia?
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3. What do the specimens of coqina and biturninous coa1 have in common? In what important ways do they
differ, relative to their origins (check the textbook)?
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