POPULATION POLICY RESEARCH AND POLITICAL SCIENCE

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Experimentally produced glass compared with that occurring at The Torr, NW Scotland, UK: vitrification through biotite melting

It is proposed that the vitrification in some Iron Age forts in NW Scotland can be explained through decomposition of micas (largely biotite) giving melts that react with or dissolve quartz and crystallise orthopyroxene and feldspars, so equating with the reaction biotite + quartz = sanidine + orthopyroxene + liquid. A sample of Moine semi-pelite has been experimentally melted at c. 850 °C demonstrating this breakdown reaction. A preserved thermal gradient across the sample reveals the progressive degradation of biotite towards the melting (upper) surface. Degradation is evident from the initial emphasis of mica cleavages in grains at the bottom of the sample, and then appearance and progressive increase in size of bubbles associated with biotite and melt towards the top of the sample. A chocolate-brown melt was produced as a coating on the upper surface and along micaceous layers. A near equivalent sample was located from the fort at The Torr that, whilst being more thoroughly affected by heat, with no unaffected biotite, preserved similar textures. Compositions of original Moine minerals are used to constrain the melts produced and melt evolution is tracked through quenched crystals. These include ternary feldspars as well as sanidine, spinels and orthopyroxene. Spot geochemical evidence demonstrates the heterogeneity of the melts, plus varying contributions of Ca and Na that could be attributed to the onset of reactions involving feldspars and other minerals from the original assemblage. It is thus concluded that a similar temperature to that of c. 850 °C derived in the experiment was reached in the vitrification process at The Torr in order to produce the glass observed.     

Mississippian religious beliefs and ritual practice: Earthen monuments,rock art,and sacred shrines

Abstract

The five books under review here explicitly call for archaeologists to place greater emphasis on agency and practice in understanding the role of religion and ritual in the ancient world. Four volumes, principally investigating Mississippian polities, draw our attention to the American midcontinent and its earthen monuments, magical plants, rock art, sacra, and sacred shrines. Although spanning a diversity of approaches and perspectives, the authors demonstrate how cosmograms, exotic objects, sacred landscapes, and transcendental beings articulate with people’s daily lives and lived experiences. Each work offers an awareness of religion as expressed through materiality and the ways past belief systems were bundled, constituted, entangled, and intermeshed with agentive things, built landscapes, humans, natural environments, and other-than-human-persons. The fifth book, by Brian Hayden, contributes a significant approach to these ongoing discussions by stressing the importance of secret societies for interpreting and understanding the power of ritual in the ancient world.