Natural Science in Archaeology

110 5 Gemstones, Seal Stones, and Ceremonial Stones
Fire opal gets its “fire” from the diffraction of light where units of silica (SiO 2 )
are arranged in a geometric pattern of the proper size to diffract light entering the
material. Fire opal first came from Europe centuries ago, with Hungary providing
the best material. The orderly arrangement of spherules of cristobalite in opal also
can impart color. “Cacholong” is a milky white or bluish white opal resembling
mother-of-pearl. It is found in Austria, Czech Republic, Iceland, Greenland, Mongolia,
and Uzbekistan. Unfotunately, this name also has been given to similar-looking
chalcedony. De Fourestier (1999) reports the name also has been used for nephrite.
Lapis Lazuli/Lazurite, (Na,Ca) 8 (Al,Si) 12 O 24 [(SO 4 ),Cl 2 ,(OH) 2 ], has a hardness of
5–5.5 and a density of approximately 2.42. It is known for its blue color, which can
vary from deep blue, indigo blue, azure blue, and violet blue to greenish-blue. The
color varies with the nature of the sulfur radicals in its structure (Leithner 1975).
Its name is derived from the Latin word for “stone” and Persian lazhward ( )
meaning blue color. In the fifth century CE, the mineral was introduced into Europe
with the name ultramarinum, which became “ultramarine.” A word of caution: the
word “lapis” comes from the Latin for “stone” so has been used as a part of many
variety names, e.g., lapis indicus is nephrite. Both Pliny and Agricola use the name
sapphiris for lazurite.
The only proven ancient source of lapis lazuli in the Old World is Badakshan,
Afghanistan, although there are unsubstantiated suggestions that there may have been
an ancient source in Iran (Von Rosen 1998). There has been some discussion about
a possible source at Latium, Italy (see Stevenson et al. 1974; Hogarth and Griffin
1975). Badakshan is mentioned in Chinese writings as early as the sixth century CE.
Lapis from Badakshan is almost always associated with pyrite. For a good discussion
of lazurite, its sources, geology, and exploitation see Kostov (2005c). New sources of
lazurite have been identified at Lake Baikal in Siberia, in Spain, and in Chile.
Lapis lazuli found its way to the Indo-Pakistani region by Neolithic times (Barthelemy
and Casanova 1993). The mines of Badakshan were described by Marco Polo, who
visited them in the thirteenth century (Bauer 1968; Leithner 1975). Necklaces of lapis
lazuli have been found in the Caucasus. Importation of lapis began as early as the 3rd
Dynasty at Ur for cylinder seals and beads. It found its way into Egypt by Predynastic
times. Biswas (1996) reports the use of imported lapis lazuli in ancient India in the seventh,
sixth, and fourth millennia BCE. Gems and seals were carved of lapis lazuli, and
it was also used for beads, small decorative objects, and paint pigments.
Talc, Mg 3 Si 4 O 10 (OH) 2 , is the softest mineral with a hardness of 1. It has a density
range of 2.58–2.83. Its name is taken from the Arabic talq ( ). It is the major constituent
of steatite (soapstone), a rock whose hardness ranges from 3 to 4 because
of other constituents. Talc is usually pale green to dark green or greenish-gray, but
white, silvery white, gray, and brownish colors are also found. According to Pliny,
steatitis came from Siphnos (N.H. 37.186; 36.159). Decorative objects, small carvings,
and beads were made from steatite. The ancient Egyptians glazed steatite
beads with a sodium or potassium-calcium silicate as early as the Badarian Period
(4000 BCE) (Andrews 1991). The steatite was heated to between 800 and 1000°C
(Vandiver and Kingery 1986). Heating dehydrates and hardens steatite up to Mohs
hardness 5 to 7 – hard enough to cut glass (Aldred 1978).