Natural Science in Archaeology

6.4 Alabaster and Gypsum 131
medium in which to keep unguents fresh (Fig. 6.4). Since Pre-Roman times, some of
the finest alabaster has come from the quarries around Volterra and Castellina, Italy.
During the Hellenistic Period, tessellated pavements using alabaster and other stones
became increasingly popular, especially in public buildings and baths.
Medieval artisans employed alabaster as a substitute for marble. It was extensively
used in the production of statuary throughout Europe (Paatz 1956; Tavender
1959). One of the major uses of alabaster was for altar carvings, and more than 3000
such pieces are still extant throughout Denmark, Germany, France, Holland, Spain,
Italy, and England. By the fourteenth century, gypsum alabaster, which is easy to
carve and gild, was being used in Western Europe (Penny 1993). Calcite alabaster
(often called “banded alabaster” or “onyx”) was also employed. Alabaster quarries
near Derby and Nottinghamshire in England provided raw material for such varied
uses as gravestones, tables, paving stones, chimney pieces, candlesticks, plates,
and bowls (Firman 1984). Other European quarries are found in Catalonia, France,
Germany, and the Netherlands (Penny 1993).
Gypsum. Gypsum is hydrous calcium sulfate (CaSO 4 ·2H 2 O). The term is both a
mineral name and a rock name. Mineral varieties include selenite, a transparent cleavable
form, and alabaster, which is massive and finely crystalline, pure white, or slightly
tinted, and translucent. The name comes from the Greek for moon-like in reference to its
reflective properties. Gypsum is a common mineral widely distributed in sedimentary
rocks, often as thick beds. The Minoans used large gypsum blocks as building stone.
Gypsum is an ancient name derived from the Greek word for plaster. Gypsum
has been widely used as a plaster. It is the raw material for plaster of Paris. When
heated to about 175°C, gypsum loses three-quarters of its water. On cooling, the
hemihydrate (plaster of Paris) can be mixed with water and spread, cast, or molded.
It then sets to a dense, rocklike mass of intergrown, needlelike crystals. The Egyptians
used this hemihydrate on the walls of tombs. This material has been used in
many countries and in every period since that time.
Gypsum was used as a mortar from the Early Bronze Age. It was similarly
employed in this manner to bond wood in ancient tombs of central Germany. During
the Bronze Age, gypsum was used for ornamental construction within the palaces
of Crete, mainland Greece, and on the islands of Zakynthos and Kephallenia (Gale
et al. 1988). About 2000 BCE, the ancient Minoans built a sandstone-paved road
extending from the southern to the northern coast of the island of Crete. The mortar
used to affix the sandstone pavement was a clay/gypsum mixture. The ceremonial
chair in the so-called throne room in the palace of Knossos is carved from gypsum,
and the later palace at Mycenae has a floor bordered with gypsum. Large sheets of
gypsum were used to cover the lower parts of the interior walls of the palaces and
houses. In the Greco-Roman Period, public and private statues were carved from
this material. Pausanias mentions that he saw a painted gypsum statue of Dionysus
in the home of a private individual (Description of Greece 9.32.1). Like alabaster,
gypsum can be cut into thin slabs and used as a light-diffusing medium, and sheets
of selenite have been found from the Roman Period. In the Medieval Period, such
“windows” were often pierced and fragments of colored glass were inserted into
the apertures.