Slate — Ipegyaq
Slate is one of the most common types of stone in the Kodiak region. This widely distributed sedimentary rock is part of the Kodiak Formation, a set of rocks the makes up the center of the Kodiak Archipelago. Slate outcrops widely from Shuyak Island to Alitak Bay. This dark grey material formed in shallow seas during the Late Cretaceous period. Millions of years later, it became an important source of material for cutting and piercing tools.
The Alutiiq word for slate, ipegkaq, literally means “one that will be sharp”. This name refers to the widespread use of slate by Alutiiq toolmakers. Kodiak slate cleaves easily, and it is soft. It breaks into flat sheets that can be snapped and ground into shapes. Experiments show you can make a tool relatively quickly by grinding a piece of slate on a harder rock with a bit of sand and some water. Alutiiq craftspeople began experimenting with slate more than 6,000 years ago. The earliest slate tools are bayonets, long, parallel-sided pieces of slate ground to a sharp point for stabbing fish and sea mammals. Over the span of Alutiiq history, slate grinding became more common and people made projectile points, end blades, ulus, knives, and even beads and labrets from slate.
Not all slate is suitable for tool making. Slate tools have a tendency to break. Kodiak’s archaeological sites are filled with ulus and points broken by people making and using slate tools. The best slate is the hardest material. It tends to be almost black and contains more silica. This makes it harder to work, but much more durable. Outcrops of these materials can be found in places where younger rocks lie next to slate outcrops. When the younger rocks formed, they heated and hardened the adjacent slate.