OBSIDIAN

Flintknapping, or the making of stone tools, uses a number of raw materials that have a variety of characteristics and qualities.  In many times and regions, obsidian has been one of the most desirable stones for its workability, as well as its beauty.  Wherever it has been found in the world it has been the focus of considerable energy to procure and transform into objects as simple as flakes, or as complex as fine blades and eccentrics.  In prehistory it was used for everyday implements, but it also played a central role in many myths and rituals.  Obsidian is also known as volcanic glass, and though it has the same silica and iron composition as granite, it is incredibly lustrous and transparent.  When felsic lava cools rapidly it is unable to develop the usual crystalline structure of stone, which results in a uniform and vitreous material.  The cutting edge produced is sharper than the highest quality surgical steel.

This stone is most commonly black, often streaked with darker bands of concentrated iron that suggest how the obsidian flow moved.  If other trace elements are present the stone will appear green, brown, orange, yellow, or as swirled combinations of these colours.  Iridescent forms are called rainbow obsidians, which are caused by the inclusion of other elements and the presence of minute air bubbles that alter how light is refracted. Over time, the unstable nature of volcanic glass will begin to correct itself, forming lighter pockets of ‘snowflakes’ until the entire piece becomes crystalized.  Due to this process, it is rare for obsidian to be older than a few million years.

Text and images by guest contributor Emma Yasui,  Phd student of archeology at the University of Toronto.