Natural Science in Archaeology

7.7 Iron Minerals 169
7.7 Iron Minerals
By the time of Agricola, early mineralogists distinguished the following iron “ores:”
hematite, magnetite, ochre, and ferrugo (limonite or rust). For a discussion on early
iron ores, see Coghlan (1956). The iron deposits of the island of Elba in the Tuscan
Archipelago have been worked for over 2000 years by the Etruscans, the Romans,
and later by others.
Hematite, α-Fe 2 O 3 . A red iron oxide, this mineral (hardness 5–6.5; density 5.26)
was used extensively throughout the world. The name comes from the Greek word for
blood-red. While the streak (the color of the finely powdered mineral, so-called because
of the diagnostic test used by geologists of drawing a mineral across a piece of unglazed
porcelain and noting the streak) of hematite is red, the mineral itself can be black or,
in the case of specular hematite, a metallic silvery color. Hematite is widely distributed
in rocks of all ages and is the most abundant and important ore of iron. Hematite
sometimes, as in the variety called specularite, has a lustrous gun-metal color and was
fashioned into ornaments. Well-crystallized hematite is tough, hard, and heat-resistant.
Engraved cylinder seals of hematite have been found in the ruins of Babylon.
The specular variety of hematite has long been valued as a gemstone. This material
is so lustrous it can be used as a mirror. In Europe, the best hematite crystals are
from the Swiss Alps and the island of Elba.
Most hematite can be ground to a good red ochre powder, a pigment that has
been used throughout history. Red ochre was a widely used pigment in the ancient
Near East. The ancient Egyptians had plentiful supplies of red ochre near Aswan
and in the oases of the Western Desert. In North America, red ochre (either as lumps
or as ground into a pigment) was used to accompany the dead in their burials. In
central and eastern North America (an area roughly bounded by Minnesota; Ottawa,
Canada; North Carolina; and Alabama), hematite was used in prehistoric times to
make pendants, axes, celts, and edged tools. Celts are the most common and widespread
hematite implements in this region. The hematite was recovered from glacial
till and from bedrock quarries.
A cylindrical silver container with an attached probe was recovered from a
noblewoman’s grave in Judea dated to the third century CE. The composition of the
tube was found to be a silver alloy with silver solder. Inside the silver tube was a red
powder composed mostly of red hematite (50%) and malachite (35%), with lesser
amounts of cassiterite (1%), galena (0.5%), and calcite (