Obsidian
"A naturally occurring volcanic glass formed as an extrusive igneous rock."
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extrapolated from a volcano cools rapidly with minimal crystal growth.
Not a “True” Mineral
Technically, obsidian is a mineraloid, not a mineral.
- Why? A true mineral (like quartz) has a crystalline structure, meaning its atoms are arranged in an orderly, repeating pattern.
- Chaos: Obsidian cools so fast that the atoms are frozen in a chaotic, disordered state—essentially a liquid frozen in time.
The Sharpest Blade on Earth
One of obsidian’s most famous properties is its conchoidal fracture. When broken, it does not crumble; it snaps into curved, razor-like shards.
- The Molecular Edge: A high-quality steel scalpel has a rough edge when viewed under a microscope. An obsidian blade can have an edge just 3 nanometers thick—that’s sharp enough to cut between individual cells. This is why some modern surgeons still use obsidian blades for delicate procedures where minimal scarring is required.
Colors and Varieties
While pure obsidian is jet black, impurities can create stunning variations:
- Snowflake Obsidian: Contains white clusters of cristobalite crystals that look like snowflakes.
- Mahogany Obsidian: Streaked with reddish-brown hematite (iron oxide).
- Rainbow/Sheen Obsidian: Trace layers of magnetite nanoparticles create iridescent gold, silver, green, or violet sheens when viewed in sunlight.
Ancient Technology
For thousands of years before the discovery of metal, obsidian was the “steel” of the ancient world.
- Trade: It was so valuable that Neolithic people formed vast trade networks to transport it hundreds of kilometers.
- Warfare: The Aztec “macuahuitl” was a wooden sword embedded with obsidian blades, said to be capable of decapitating a horse.
- Dating: Archaeologists use Obsidian Hydration Dating to determine the age of artifacts. By measuring how much water the fresh surface of a broken tool has absorbed from the air, they can estimate when it was made.
FAQ
Q: Is “Dragon Glass” real? A: Yes! In “Game of Thrones,” Dragon Glass is based on obsidian. While real obsidian can’t kill White Walkers, its use as a weapon against “cold” enemies is a nod to its volcanic (fire) origins.
Q: Is it true that obsidian is in Minecraft? A: Yes, obsidian is a famous block in the game Minecraft, formed when water hits a lava source block. It is known for being incredibly hard to break (requiring a diamond pickaxe) and is used to build portals to the Nether dimensions. This has introduced a generation of young people to igneous petrology!
Q: Where can I find it? A: You can find it in areas with geologically recent high-silica volcanism, such as Glass Buttes (Oregon), Obsidian Cliff (Yellowstone), and parts of Iceland, Italy, and Japan.
Surgical Precision
Research has shown that obsidian scalpels cut with far less pressure than steel, causing less damage to the tissue cells surrounding the incision. This leads to faster healing and less scarring. However, because obsidian is brittle and can break inside the patient, it is not FDA-approved for general use and remains a niche tool for specific cosmetic or experimental procedures.