Hickory Bluff Project
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Issue 6: Hearth Stones or Pot Boilers?
The stones that are found in the hearth features at the Hickory Bluff site may have been used in a variety of ways, some obvious and some not. The most obvious use is implied in the name hearth stone. These rocks were used to line fire pits or were placed around a fire to contain it or to be used as holders or trivets. Stones were also used frequently in roasting platforms. Here they were laid on the fire to absorb heat and release it at a controlled rate.
Another, less obvious use for heated rock was to indirectly boil liquids. The technique of stone boiling or pot boiling is common among populations which do not have containers that could be placed directly in a fire. A liquid was put in a container of material such as wood, skin, or a tightly woven or clay-lined basket. Stone cobbles were heated in a fire and dropped into the liquid. The stones quickly cooled, and as they did, their heat was transferred to the liquid, causing it to boil in relatively little time.
Illustration courtesy of Herbert
Archaeologists have reproduced this process experimentally in order to study the results. Rocks used in stone boiling are rapidly cooled as they are immersed in liquid. In comparison, stones used in hearths or as roasting stones will usually cool more slowly. Patterns have been observed in experimental results in which slow-cooled hearth stones tend to crack less often or to split into large fragments, while rock used repeatedly for stone boiling will exhibit a crackled or crazed surface and tend to break into small pieces.
One of the ways we are investigating the original use of stone from the hearth-like features at the Hickory Bluff site is by examining the average weight of the fragments. If they are large, they are likely to have been used as hearth stones; if small, they are more typical of highly fragmented boiling stones.
