Download Classifying Common Sedimentary Rocks

Earth Science
Name ________________________ Per.___
Classifying Common Sedimentary Rocks
Sedimentary rocks may be classified into three groups based on what they are
made of and how they were formed. If the sediments that make up the rocks came
mostly from the shells or body parts of living things, the rocks would be classified as
organic sedimentary rocks. If the sediments were produced from minerals that
were dissolved in water but later came out of solution, the rocks would be classified
as chemical sedimentary rocks. When elements come out of solution, the elements
are said to have precipitated and the process is called chemical precipitation.
Chemical sedimentary rocks are also called evaporites. If the sediments were
formed from particles that were weathered (broken off) from other rocks, the
rocks are called clastic sedimentary rocks. Clastic sedimentary rocks are classified
on the basis of the size of the sediment particles that the rock is made of.
The chart of sedimentary rocks summarizes the characteristics of the most
important types of sedimentary rocks.
Common Sedimentary Rocks
Sedimentary Rock Type
1. Organic Sedimentary Rocks
Formed from the remains of living
things such as plants or animals.
Limestone comes from tiny animals
in the ocean. Coal comes from
plants that grew in swamps.
2. Chemical Sedimentary Rocks
Formed when minerals that were
dissolved in water come out of
solution. Minerals can be
dissolved from rocks into ground
water, and then transported
somewhere else where they can
form a new rock.
3. Clastic Sedimentary Rocks
Formed when the particles that
are weathered (broken off) from
other rocks are cemented
together to form a new rock.
Particle Size or Composition
mostly shells of tiny animals
mostly plant remains that are
millions of years old
Sediment particles are too small
to be seen without a microscope.
The dissolved mineral that comes
out of solution determines the
rock that is made:
Calcite
Mineral:
Dolomite
Halite
Gypsum
Rock Name
Limestone
Coal
(bituminous)
Rock type
formed:
Limestone
Dolomite
Rock Salt
Gypsum
Particle Size:
boulder-sized (greater than 256 mm)
cobble-sized (64 to 256 mm)
Conglomerates
pebble-sized (2 to 64 mm)
sand-sized (0.06 to 2 mm) Sandstone
clay-sized (less than 0.06 mm) Shale
Refer to the chart on page 1 to complete the Data Table and answer the questions.
1. Read the description and fill in the correct Sedimentary Rock type.
DATA TABLE
Description
Sedimentary Rock Type
Rock Name
a. The sediment particles are formed by
chemical precipitation and are too
small to see without a microscope.
b.The sediment particles are mixtures of
sizes that range between 3.0 mm and
20.0 mm.
c. The sediment particles are pieces of
shells.
d. The sediment particles are
sand-sized.
e. The sediment particles are mostly
parts of plants.
2. a. What sedimentary rock can be formed in two different ways? ______________
b. Describe the two ways that this rock can form _________________________
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3. What is the only sedimentary rock type that can be formed from things that were
once alive? _____________________________________________________
4. Table salt you put on your food is made of the mineral halite. What sedimentary
rock is also made of halite? __________________.