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? __________________.