Obsidian

High school (ages 12+)
Environment & Earth

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/obsidian

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the rock type?Extrusive igneous rock (volcanic glass)
2. What is the composition?Rich in felsic elements such as silicon, oxygen, aluminum, sodium, and potassium
3. What is obsidian and how does it form?Obsidian is a shiny black volcanic glass that forms when hot, silica‑rich lava cools extremely fast, freezing the atoms before crystals can grow.
4. Why is obsidian so sharp?Because its atoms are arranged randomly, not in crystals, so when it breaks it makes edges only a few atoms thick, giving it a razor‑thin edge.

Amorphous: Lacking a defined shape or structure; without crystalline order.
Viscosity: A measure of a fluid's resistance to flow; its thickness or stickiness.
Conchoidal Fracture: A type of fracture that produces smooth, curved surfaces, characteristic of glassy materials.
Nucleation: The initial stage of crystal formation, where small clusters of atoms begin to form.