Natural Science in Archaeology

11.2 Building Stone 255
“Basaltina” is a unique Italian light gray basalt with specks of volcanic ash that
has been used as an elegant building stone for more than 1000 years. Basaltina has
a dense and uniform structure and is frost resistant. It has been a common building
stone in Umbria, Italy.
11.2.4 Limestone/Sandstone
The first use of the term “limestone” was in the literal sense: a stone from which
lime could be extracted. In modern geologic usage, the term limestone includes
sedimentary rocks composed of 50% or more calcium carbonate. Most limestones
exploited throughout history contained more than 90% carbonate. Limestones form
in several ways. They may be detrital, chemical precipitates, or biogenic (often made
up largely of shells). The outer facing of the great pyramids of Egypt is limestone.
The great Gothic cathedral at Chartres, France (begun in 1194 CE), is constructed
of limestone. Limestone was used by the Inca to construct Sacsahuaman (ca. 1500
CE), a fortification built of megalithic polygonal blocks (Von Hagen 1961). Another
example of a well-known site that was constructed of limestone is ancient Troy
near the Aegean Sea in northwest Turkey. I worked at Troy on and off for many
years. (Rapp and Gifford 1982) The massive walls and structures were built from
the abundant local bedrock limestone. (Fig. 11.5)
Tufa is another rock that is composed principally of calcium carbonate. It
forms when calcium carbonate is precipitated out of water near hot springs or
along shorelines. Large deposits of tufa are found in Italy, and these deposits
Fig. 11.5 The author inspecting the walls of ancient Troy built out of the local bedrock limestone
(Rapp 1982)