How Gemstones Are Formed: 10 Interactive MCQs on Rock Origins

Continue the book-based quiz series with How Gemstones Are Formed. These 10 questions follow the book’s explanation of the rock cycle, igneous and metamorphic rocks, sedimentary deposits, and organic gems. Select an answer for each item and submit for instant scoring and explanations.

10 questions · Four options each · Instant results

1. Which set names the three main rock types described in the book?

Plutonic, volcanic, and crystalline
Igneous, sedimentary, and metamorphic
Mineral, organic, and synthetic
Intrusive, extrusive, and alluvial

2. How does the book describe the formation of igneous rocks?

By shells accumulating on the seafloor
By weathered fragments hardening in layers
By heat and pressure changing existing rocks
By molten rock cooling and solidifying

3. Which materials does the text associate with extrusive igneous rocks?

Lava, volcanic bombs, or ash erupted from volcanoes
Only rocks transformed deep underground
Layers of shells and coral
Tree resin and fossilized wood

4. Where do intrusive igneous rocks solidify?

In river gravel only
At the surface after weathering
Beneath the surface
Inside living shellfish

5. What happens to crystal size when igneous rock cools more slowly?

Crystals cannot form
Larger crystals can form
Crystals become sedimentary layers
The rock turns into organic material

6. Which rock type is noted as a setting for many large gemstone crystals?

Shale
Marble
Mica schist
Pegmatite

7. What process forms metamorphic rocks, according to the book?

Heat and pressure alter existing igneous or sedimentary rocks
Molten rock erupts and cools at the surface
Tree resin fossilizes in sediment
Shellfish form pearls around foreign bodies

8. Which example of gemstone formation in metamorphic rock appears in the text?

Amber in volcanic ash
Pearl in marble
Garnet in mica schist
Turquoise in pegmatite

9. What does the book say about marble and rubies?

Marble forms from lava and always contains rubies
Marble forms from limestone changed by pressure and heat, and may contain rubies
Rubies form as fossils inside marble shells
Marble is a sedimentary gem gravel

10. Which statement about sedimentary rocks and gems is correct?

They form from molten rock; most Australian opal is in pegmatite
They form by heat and pressure; turquoise occurs only in marble
They form from tree resin and are always unlayered
Weathered fragments accumulate and harden, commonly in layers; most Australian opal occurs in them

Source: Cally Hall, Gemstones, “How Gemstones Are Formed,” pp. 12–13. Questions are paraphrased from the book.