Obsidian

Obsidian is a natural volcanic glass formed when silica-rich lava cools so fast that crystals cannot form. It fractures into razor-sharp edges and can be shaped into precise cutting tools.

Description of what it is like

It is usually black or dark brown with a glossy, glassy surface. It feels smooth, is brittle under impact, and breaks with conchoidal fractures that create sharp edges.

Origin and where to find it

• Environments: Volcanic regions, lava flows, and rhyolitic domes.
• Signs: Shiny black fragments or glassy nodules mixed with volcanic rock.
• Natural: Forms directly from rapid lava cooling.

Minimum processing required

• Selection: Choose dense, glossy pieces without visible cracks.
• Knapping: Strike controlled flakes to expose sharp edges.
• Retouching: Pressure-flake to refine cutting edges or points.

Tools needed to work on it

• Hammerstone: For initial flakes.
• Antler or bone pressure flaker: For edge refinement.
• Leather pads: Hand protection and grip.
• Abrasive stone: Smoothing or dulling unsafe edges.

Common forms of use

• Flakes and blades: Knives and scrapers.
• Points: Arrowheads and spear tips.
• Ornaments: Beads or polished pieces.

Possible substitutes

• Flint: Similar sharpness, more common in many regions.
• Stone: Works for blunt tools but less sharp.
• Bone: Lighter tools and needles, but less durable.

Limitations and common failures

• Brittleness: Shatters under impact or bending forces.
• Edge fragility: Extremely sharp but chips easily.
• Heat sensitivity: Can crack if heated unevenly or shocked.

Risks and safety

• Cuts: Edges are sharper than steel scalpels.
• Shards: Flying flakes can injure eyes or skin.
• Dust: Fine particles from knapping can irritate lungs.

Related materials

• Glass: Similar amorphous structure.
• Flint: Another knapping stone.
• Stone: Common host and alternative.