Natural Science in Archaeology

7.8 Tin (Sn) Minerals 171
now somewhat out of date, is presented by Still (1946). The Chinese were the first
to use lodestone (magnetite) as a compass. The Mesoamerican Olmec “compass”
was made of hematite (see Carlson 1975).
In parts of Europe, siderite (FeCO 3 ) was also exploited as an iron ore. It was
called chalybite, a name derived from Chalybes, an ancient nation in Asia Minor
famed for skill in iron-working.
7.8 Tin (Sn) Minerals
The chemical symbol for tin, Sn, is derived from its Latin name stannum. The word
tin likely derives from the German zinn. Tin only occurs rarely and in very small
quantities as a native metal. Its chief importance in antiquity was as a component
(about 10%) with copper in bronze and with lead in pewter. Tin bronze is harder and
has greater tensile strength than copper, important for weapons, and greater fluidity
in the molten state, important for casting. Tin came into medical use in the Middle
Ages as an agent for expelling intestinal worms, a remedy recommended by Paracelsus.
Tin metal is relatively soft, but, with small amounts of other metals added to
make an alloy, it becomes sufficiently durable for domestic use. However, even the
alloys had low melting points (170–230°C) so were not suitable for cooking pots.
For a thorough review of our knowledge of tin in antiquity (through the early 1980s),
see Penhallurick (1986). The scope of Penhallurick’s book is basically worldwide. He
covers Africa and Asia, but concentrates on Europe. A now somewhat dated overview
of tin in the ancient world is available in Franklin et al. (1978). The literature is full
of misinformation, or at least uncritical reporting, concerning ancient tin sources. For
example, Wilson (1994:18) presents a map of “mines of the Middle East”. On this
map, tin mines are shown near Eskisehir and Erzincan, Turkey. I have visited this area,
and there is no evidence for significant tin in regional geologic formations.
Cassiterite (SnO 2 ) (sometimes called stream tin or wood tin) has a hardness of
6.0–7.0 and density of 6.99. It is the only important ore of tin. Stannite (Cu 2 FeSnS 4 )
is fairly widely distributed, but there is no evidence that it was exploited in the
ancient world and it is not economically important in the modern world. The name
cassiterite comes from the Greek word for tin, kassiteros. Cassiterite is found in
granites, pegmatite dikes, and quartz veins. It is also found in high-temperature
hydrothermal veins in or near granite. It is liberated from these primary deposits by
disintegration of the host rock. Because of its high density and resistance to weathering,
cassiterite becomes concentrated in gravel and placer deposits. The original
recovery of cassiterite is likely to have been from such placer deposits. One can
only wonder how early miners distinguished small grains of black cassiterite from
those of magnetite, which is also black and has high specific gravity. Many placers
are called “black sand” because of the predominance of magnetite. Cassiterite
is sometimes also associated with gold in placer deposits, which may have been
the reason it was first noticed. Tin becomes molten at 232°C and occasionally was
used in its metallic form in the ancient Old World. For the geology and mineralogy