Árbók Hins íslenzka fornleifafélags - 2019, Blaðsíða 150

149FERÐASAGA MÓSAÍKFLÍSA – PORFÝRSTEINAR Á ÍSLANDI
Summary
The travel‒log of mosaic tiles – porphyry in Iceland
A total of six artefacts of green porphyry, porfido verde antico, and one of red, porfido
rosso antico, are known from Iceland. These porphyry artefacts are some of the
oldest, and most widely traveled artefacts in the Icelandic assemblage. Porphyry
is an igneous rock with large-grained crystals, often of feldspar or quartz. The
origins of the green and red porphyry stones can be traced to Greece and Egypt
respectively, where they were quarried until the 5th century AD, and were priced
for decorative purposes within the Roman Empire such as for opus sectile f loors
and wall decoration as well as imperial statues and sarcophagi. Porphyry was
reused from Late Antiquity and well into the Middle Ages with reused porphyry
stones, or spolia, having been found in North-Western Europe in medieval
contexts. Porphyry artefacts were introduced into Icelandic material culture in
the 11th century and were in circulation until the beginning of the 20th century.
The typology of the Icelandic porphyry stones can be placed into two categories:
f lat and elongated stones, but both forms are considered to derive from their
prior function in the Roman context, most likely as opus sectile f loor and wall
decorations. In this paper the Icelandic artefacts are viewed within the framework
of porphyry research in North-Western Europe, but most of the Icelandic artefacts
are considered to have been used as altar stones, although the use of the elonged
stones from Viðey and Reyholt has remained unclear. The porphyry stone from
Viðey is here interpreted as not having been used as an altar stone, rather that it
was some sort of tool, perhaps a mortar pestle or for smoothing wax tablets due
to its context, wear and relation to other elonged stones from the site with similar
wear. This gives an indication that porphyry stones might not have solely served
a liturgical role in Iceland but might in some cases have served other functions.