Minerals and the Three Rock Families · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading a rock like a geologist

Science · Earth's Systems · ages 14-15
Name ______________________   Date ____________

  1. Two rocks share the same colour. What should you study to tell their families apart?

    • Colour: trust the brighter shade
    • Size: trust the heavier rock
    • Texture: crystals, grains and layers

  2. A rock is full of interlocking crystals. How did it form?

    • Melt cooled and hardened
    • Grains were pressed and glued
    • An older rock was squeezed and heated

  3. Sandstone holds separate grains pressed and glued together.

    Circle one:   True   False

  4. A sandstone holds rounded grains that all match in size. How far did they travel?

    • Far, sorted and rounded on the way
    • Barely moved, broken off nearby
    • Melted, then frozen in place

  5. An igneous rock has tiny crystals you can barely see. Where did it cool?

    • Slowly, deep underground
    • Fast, at the surface
    • Under squeezing from one side

  6. A shiny banded rock that splits into flat sheets is probably sedimentary.

    Circle one:   True   False

  7. A student calls a rock sedimentary because it is red. What is wrong with that call?

    • Colour alone cannot name the family
    • Red rocks are always metamorphic
    • Sedimentary rocks are never red

  8. Two granites share minerals, but one has large crystals and the other tiny ones. What differs?

    • Their colours
    • Their mineral lists
    • Their cooling histories
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading a rock like a geologist W1-mt_S0edEKh084-s1

  1. Texture: crystals, grains and layers · Texture tells the story of formation. Colour alone misleads.
  2. Melt cooled and hardened · Interlocking crystals grow as melted rock cools and hardens into granite.
  3. True · Separate grains stuck together is the mark of sandstone, a sedimentary rock.
  4. Far, sorted and rounded on the way · Long travel rounds grains and sorts them to match. Short travel leaves them mixed.
  5. Fast, at the surface · Tiny crystals mean fast cooling. Slow deep cooling grows big ones.
  6. False · Shine plus bands plus flat splits means metamorphic, not sedimentary.
  7. Colour alone cannot name the family · Any family can wear red. Only texture can name the family.
  8. Their cooling histories · Same minerals, different sizes: one cooled slowly deep down, the other fast above.
Worksheet · LightMySky