Natural Science in Archaeology

5.5 Oxide Minerals 115
quoise has been recovered from other sites in Chaco Canyon dating to the period
900–1150 CE (Mathien 2001). Turquoise was a major commodity in Mexico from
the late first millennium BCE through modern times. Cortez reported that Aztec
chieftains wore turquoise stones in their lower lips. There were numerous turquoise
mines in northern Mexico (Weigand 1994).
In Precolumbian Mesoamerica, worked turquoise artifacts are abundant throughout
its prehistory beginning in the early Preclassic (ca. 2000–1000 BCE). Its possession
signified the status of nobility. Through neutron activation analysis it has
been established that much of the turquoise found in Mesoamerica had its origin in
the American southwest and the northern part of Mexico (Harbottle and Weigand
1992). It was used in jewelry and as inlay in ceremonial shields and mosaics. Perhaps
the most famous artifact of Mesoamerican turquoise is the turquoise-covered
mask of Quetzalcoatl made between the fourteenth and fifteenth century, and now in
the Museum of Mankind in London (Lehman 1906). For a more extensive treatment
of turquoise mosaics, see Saville (1922) and Carmichael (1970).
Spinel, MgAl 2 O 4 , has a hardness between 7.5 and 8 and a density of 3.58. Spinel
varies in color from red, blue, green, brown, to black. Its name is from the Latin
spinella (little thorn). It was probably mined early in antiquity, but the distinction
between spinel and ruby was not made until Arab scholars learned to use specific
gravity to distinguish spinel from ruby in the eleventh century, and even after this
was probably not widely applied (Sersen 1995). In Europe, this distinction was
made during the nineteenth century. Until recently, this mineral was often confused
with ruby. Arab scholars identified this stone as originating in Afghanistan as early
as the tenth century. Pliny refers to red stones by the general term carbunculus.
This may have included red spinel. He lists sources as India, North Africa, Caria,
Ethiopia, Miletus, Orchomenos, Chios, Corinth, Troezen, Marseilles, and Lisbon
(N.H. 37.91, 92–98, 103, 122, 123). Spinel was used as a gemstone.
Corundum, Al 2 O 3 , with a hardness of 9 is one of the hardest minerals known.
It has a density of 4.05 and is found in several varieties. It occurs widespread in
crystalline limestone and dolomite, schists and gneisses, and granitic igneous rocks.
The name corundum comes from the Tamil word kurundum. Ruby and sapphire are
the gem varieties of this mineral.
Ruby. Red in color, ruby takes its name from the Latin rubeus (red). The red
color arises from the replacement of some Al 3+ atoms by Cr 3+ . According to medieval
Arab scholars, this stone (yaaqut, ) was mined in Sri Lanka (Sersen 1995).
Pliny refers to red stones by the general term carbunculus. He lists sources as India,
North Africa, Caria, Ethiopia, Miletus, Orchomenos, Chios, Corinth, Troezen,
Marseilles, and Lisbon (N.H. 37.91, 92–98, 103, 122, 123). It was used as a gemstone
and possibly as a cutting or engraving tool. Although ruby is mentioned in
some translations of the Old Testament, there is no evidence that this mineral was
known to the ancient Hebrews.
Sapphire. This variety is found in blue and yellow colors. Its name is an ancient
term of uncertain origin, possibly related to Hebraic sappir and Sanskrit sanipruja.
Pliny’s chrysolithus from India may have been yellow sapphire (N.H. 37.90, 91,
101, 126, 127). Leucochrysus may have also been yellow corundum. Pliny does not