3. At meal time, you simply pick up
your metal utensils and begin. What
did people use before such tools
were available? In this activity, we’ll
explore how characteristics of one
rock played a role.
5. Step 1
• Discuss the following question with your
research team, “Can a rock be used as a
knife?”
• Make notes about your discussion,
explaining the reasons for your answer.
(Your team may or may not agree. What is
important is to explore ideas.)
6. Step 2
• Carefully examine the piece of obsidian (a
kind of volcanic rock) that your teacher
gives you.
• Add additional notes to your journal
supporting or changing your original
prediction.
• Explain your reasons.
7. Step 3
• Pick up the apple.
• Use the obsidian to try to cut off a piece of
skin - the apple’s, not yours! (Be careful!
Obsidian can cut fingers as easily as fruit.)
• Be sure each member of your team gets a
turn using the “Razorblade Rock” to cut
the apple.
8. Step 4
• Clean up your work area and return the
“Razorblade Rock” to your teacher.
• List some ways primitive people might have
used obsidian and similar materials.
• Now share and compare observations with
your research team.
11. Igneous Rock
• Igneous rock is formed
from the rapid cooling of
rock that was once
molten (melted).
• Molten rock usually
comes from volcanoes.
• Obsidian cools so
quickly that it takes on a
glass-like structure.
15. Obsidian Long Ago
• In the ancient world,
obsidian was considered
a valuable jewel.
• The Egyptians
considered in valuable
because it was so rare.
• Ancient people used it
for knives, arrow heads,
and spear points.
16. Obsidian Today
• Some surgeons use very
fine scalpels for surgery.
• Because it is so sharp, it
leaves scars that heal
more easily, leaving less
scar tissue, and less
infection.
17. For the word of God is living and
active. Sharper than any double-
edged sword, it penetrates even to
dividing soul and spirit, joints and
marrow; it judges the thoughts and
attitudes of the heart.
