The Hauraki region has a number of stone resources used by Maori (Fig. 12). In this respect, the area was particularly well endowed. Basalt and obsidian sourced to the Coromandel area were important stone types and have been found in sites up to 300 km away, suggesting an extensive trade in both finished tools and unmodified stone.
A variety of tools were made from stone: adzes, weapons (paw onewa), flax beaters (patu muka), scrapers and cutting tools, drill points, sandstone files, grindstones and hammerstones to name a few In addition some types of rock were highly suitable for use as hangi stones.
The rocks have been formed by different processes and vary in chemical composition. Hardness, flaking ability, or the uniform nature of the rock made some stone types particularly desirable. For example, diorite, because of its hardness, was sometimes used as a large hammerstone for splitting softer stones.
Obsidian
Volcanic glass or obsidian (tuhua or mataa tuhua) is found in only a few localities on the east coast of the Coromandel Peninsula and on Great Barrier Island (Fig. 12). Obsidian from Mayor Island, the main source, is found throughout New Zealand. Other sources include Northland near Kaeo and the central North Island (Fig. 13). The different sources can be distinguished by chemical analysis and sometimes by colour. For instance, all Mayor Island obsidian is green while the Coromandel sources tend to be grey or greenish grey. However the Northland obsidian is also green and the central North Island material is grey. It is therefore difficult to be certain by colour alone that the obsidian is from a particular place. Other characteristics of the stone (such as the presence of banding or crystals within the glass) narrow down the range of possible sources present within any one site.
On the Coromandel Peninsula obsidian most often occurs as cobbles in stream beds or on beaches and is associated with Minden Rhyolites. Sources which appear to have
