Stone Type: Obsidian

Obsidian Macroblade core, Azerbaijan

Obsidian is a volcanic glass that forms when lava cools so rapidly that the atoms are unable to organise into crystals. Obsidian occurs from a specific form of lava and the composition is similar to rhyolite and granite.  The glass can recrystallise over time, leading to patches of white crystobalite crystals within the glassy matrix. 

Biface, Simon Greenwood

Modern Art, Simon Greenwood

Flenniken biface

Modern Art, J. Jeffrey Flenniken

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Modern Art, Ted Orcutt

Multiplatform core, Azerbaijan


Aztec pressure blade core re-do 1

Blade Core

Obsidian Aztec blade


Mataa Point 1

Mata’a Point

Mataa Point 2

Mata’a Point

Macroblade core, Azerbaijan

Macroblade Core

Macroblade knife, Papua New Guinea

Macroblade Knife

An iridescent sheen can occur in obsidian caused by light reflecting from minute inclusions of minerals, debris, or gas.  Most obsidian is black but it can occur in various shades of brown, tan, green, red, blue, or yellow, depending on trace elements.  Obsidian is an excellent material for flaking, although it is more fragile than chert.  The edge of an unmodified obsidian flake is sharper than a modern steel surgical scalpel.