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    Rocks and Minerals by UTH Rocks and Minerals by UTH    

Lesson 31: Biologic Rocks


Biologic rocks are sedimentary rocks created from the remains of living organisms that have died, accumulated, and then pressed and cemented together. Examples of biologic rocks include chalk, diatomite, coal, and coquina.

Chalk: Chalk is a soft, white, powdery limestone formed by the accumulation and cementation of tiny plates of calcium carbonate formed by tiny living algae called coccolithophores. Note: The biologic chalk (calcium carbonate) is often a different type of chalk than the colored sidewalk chalk used by children (calcium sulfate).
A Chalk Formation in England
Diatomite: Diatomite is a light, powdery sedimentary rock formed from the skeletons of diatoms. Diatoms are a group of minute unicellular algae having a siliceous covering.
Coal: Coal is a black rock formed from prehistoric plant remains, composed largely of carbon and burned as a fuel. Coal is formed by the following process: Over time, the peat becomes deeply buried, where it is is subjected to heat and pressure. Over time, the peat becomes coal.

  1. Plant matter decays to form peat. Peat is soil formed of dead but not fully decayed plants found in bog areas, often burned as fuel.
  2. Some of the peat becomes deeply buried, where it is is subjected to heat and pressure.
  3. Over time, the heated and pressurized peat transforms into coal.

Coquina: Recall that coquina is made out of shells that are cemeted together.

    Rocks and Minerals by UTH Rocks and Minerals by UTH    

Lesson 31: Biologic Rocks

Directions

Study the lesson for one week.

Over the week:

  • Read the lesson.
  • Review the synopsis.
  • Recite aloud the vocabulary words and their definitions.
  • Study the rock and mineral of the week.
  • Complete the enrichment activities.
  • Study the review questions.

Synopsis

Biologic rocks are sedimentary rocks created from the remains of living organisms that have died, accumulated, and then pressed and cemented together. Examples of biologic rocks include chalk, diatomite, coal, and coquina.

Vocabulary

Biologic Rocks: Sedimentary rocks created from the remains of living organisms that have died, accumulated, and then pressed and cemented together.
Diatomite: A fine, powdery Earth formed from the skeletons of diatoms.
Diatom: Any of a group of tiny single-celled algae having a siliceous covering.

Rock or Mineral of the Week

Overview
  • Diatomite is a sedimentary rock formed from the cemented skeletons of tiny creatures named diatoms.
  • See below a view of diatoms through a microscope.
  • Diatomite is also known as diatomaceous earth and forms a white powder when crumbled.
  • Diatomaceous earth is used to kill or deter insects, as an abrasive in toothpaste, in dynamite, and as a growing medium for plants such as bonsai trees.

Physical Characteristics
  • Color: White
  • Hardness: 1
  • Luster: Dull
  • Cleavage: None
  • Streak: White
  • Tenacity: Crumbly to brittle

Enrichment

Activity 1: Narrate the Lesson

  • After reading or listening to the lesson, narrate the lesson aloud using your own words.

Activity 2: Can You Find It?

Find the following elements on the periodic table:

  • Silicon (Si)
  • Oxygen (O)
  • Hydrogen (H)
  • In which group and period is hydrogen (H)?

Activity 3: Take a Nature Walk

  • Embark on a nature walk.
  • Collect one rock or mineral specimen.
  • Use the gathered specimen to create the field book entry.

Activity 4: Complete a Field Book Entry   

After your nature walk, complete page 6 in 'Fifth Grade Science Rocks and Minerals Notebook Pages.'

Review

Question 1

Describe something about diatomite.
1 / 3

Answer 1

Diatomite is a sedimentary rock formed from the skeletons of diatoms.
1 / 3

Question 2

Is diatomite an igneous, metamorphic, or sedimentary rock?
2 / 3

Answer 2

Diatomite is a sedimentary rock.
2 / 3

Question 3

Which rock group includes those that are formed by deposition, precipitation, and biological activity?
3 / 3

Answer 3

The sedimentary rock group includes those that are formed by deposition, precipitation, and biological activity.
3 / 3

  1. Describe something about diatomite. Diatomite is a sedimentary rock formed from the skeletons of diatoms.
  2. Is diatomite an igneous, metamorphic, or sedimentary rock? Diatomite is a sedimentary rock.
  3. Which rock group includes those that are formed by deposition, precipitation, and biological activity? The sedimentary rock group includes those that are formed by deposition, precipitation, and biological activity.

References

  1. 'Sedimentary rock.' Wikipedia. en.wikipedia.org/wiki/Sedimentary_rock. n.p.
  2. 'Diatom.' Wikipedia. en.wikipedia.org/wiki/Diatom. n.p.
  3. 'Diatomite.' Wikipedia. en.wikipedia.org/wiki/Diatomite. n.p.
  4. Cited Physical Properties. Geology.com. geology.com/rocks. n.p.

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