![]() Thus, if goethite is heated to 1000 ☌, complete recrystallization occurs. ![]() As the rearrangement occurs in the solid state, the movement of ions and the release of water are impeded by the rigid crystalline matrix. We conclude that strategies other than powder XRD are necessary to draw conclusions about the ancient processing of iron ochres.ĭuring the transformation of goethite, water is lost, and the remaining iron and oxide ions must rearrange themselves into the crystalline pattern of hematite. Furthermore, by replicating the process using Stone Age technology, we show that heating goethite in a wood fire complicates the interpretation of XRD line widths of the resulting hematite. Although chemically identical, natural goethite is physically different from and much more variable than goethite produced in a laboratory. We now show that to be an inappropriate model. Measuring the line widths of powder X-ray diffraction (XRD) in hematite has been explored, and synthetic goethite heated in a modern furnace has been used as a model system for studying this process. Thus, there is a need to distinguish natural hematite from hematite generated by heating goethite in a wood fire. ![]() This represents an important cognitive and technological advance in early human prehistory. Hematite, the mineral that gives color to bright red iron ochres, occurs naturally, but there is much evidence that early humans sometimes artificially produced hematite by heating a related mineral, goethite, in wood fires.
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