In
archaeology,
fire-cracked rock is rock of any type that has been altered and split by deliberate heating. It is a feature of many
archaeological sites, particularly in the south-central
United States. In many cases, FCR results from stones being used to line
hearths or from being heated to provide a longer-lasting heat-source (similar to historic water bottles). In other cases, FCR results from stone being used to heat water; this occurs when the stones are heated and dropped directly into containers made of skin or
pottery, thus boiling the water. Central
Texas in the
United States is well-known archaeologically for its burnt-rock
middens[?], piles of FCR -- often exceeding several tons of material -- which resulted from the wholesale processing of
oak acorns during prehistoric times.