Dust is a significant, albeit under-recognized, component of patinas that accumulate on exposed surfaces of artifacts. Dust storms are ubiquitous in the Levant, often containing minerals, microfossils, and pollen which can be found within the patina of an artifact, preserving its geological signature. Archaeological materials that are exposed to local environmental and depositional processes in a tel, a cave, or soil, may accrete in a patina over time and may have some dust components reflective of the environmental record. Modern anthropogenic aerosol sources are often characterized by the presence of heavy metals. Pollen from fruits and shrubs that is not indigenous, if found in the patina, can be used to differentiate recent artifacts from those of antiquity. The scores of unprovenanced looted antiquities have necessitated the need to differentiate a genuine artifact from a modern fraud. Since the geological component of the dust in the Levant is known, and the climate and its attendant wind patterns apparently were quite constant during recent millennia times, the dust in the patinas of a true artifact is easy to differentiate from patinas containing modern dust. Both contemporary and historical dust can serve as tools to authenticate an artifact. The well-known unprovenanced, Jehoash inscription tablet, the James ossuary, and the inscribed ivory pomegranate preserved in their patinas microfossils and particles reflective of the geological environmental dust which strengthens the contention that their inscriptions are authentic.
By E. Ganor, J. Kronfeld
Department of Geophysics and Planetary Sciences,
Tel Aviv University, 69978, Ramat Aviv,
Tel Aviv, Israel.
H. R. Feldman
American Museum of Natural History,
79th Street at Central Park West, New York, NY 10024, USA
A. Rosenfeld and, S. Ilani
Geological Survey of Israel,
30 Malkhei Israel St. Jerusalem, 95501, Israel
The ability to authenticate archaeological artifacts is of critical importance. If the exact provenance of an archaeological artifact is not certifiably obtained from an official excavation, its authenticity may be suspect. Thus, archaeologists are at times confronted between choosing to limit their data base to only material exclusively obtained from an official excavation and widening their historical sources by including artifacts that have the potential of being historically significant but are not well provenanced. A notable example of the latter would be the Dead Sea Scrolls. Many of the ancient sites in the Middle East have been extensively looted. Many artifacts are unprovenanced and are
found in private collections and even in museums (e.g., the Amarna Letters from Egypt are now exhibited by many museums worldwide). The problem then is how to differentiate a genuine artifact from a modern fraud. One archaeometric method would be to study the patina that has accreted on the surface of the artifact over time. This, of course, presupposes that one knows what to expect in the patina for validation. We wish to discuss components that should be contained in genuine patinas of archaeological artifacts from arid or semi-arid lands or, conversely, what may be contained or lacking in modern forgeries. Previous work in this field has been sparse. Ayalon et al. (2004) Goren (et al., 2004, 2005) and Ilani et al. (2002, 2008) have studied the patina of unprovenanced artifacts.
As modern Israel and the historical Holy Land, including the Sinai Peninsula, are generally dry and dusty, wind-blown dust should be a ubiquitous component incorporated into accreting patinas, both historical and modern. In this study, we summarize results based on years of sampling and investigating modern atmospheric dust from various regions of Israel and Sinai that contribute components to the total atmospheric dust budget. The regional dust may be useful in readily differentiating genuine artifacts whereas the local contribution of dust particles can aid in determining provenance on a finer scale. Some of the components of modern dust should be similar to past components, whereas others are restricted to modern times and thus should not be present within the patina of authentic archaeological artifacts.
MATERIALS AND METHODS
Over the course of this study, dust was collected from 27 sites in Israel and Sinai (Fig.1; Ganor et al., 2007, 2009). Atmospheric, transported, and precipitated dust were collected: (A) at ground level, (B) by collectors on the roof of the Department of Geophysics and Planetary sciences of Tel Aviv University , and (C) at a height of 850 m via airborne collectors. Our dust sampling in Israel and Sinai (Ganor et al., 2009, Fig. 1) has been systematic and was collected every month for five years (Ganor, 1975). The methods of collection and methods of study including the travel paths and points of origin of the dust brought to Israel, the meteorological conditions and the sedimentation processes are described and discussed (Ganor et al., 1975; Ganor et al. 1991, 1995; Ganor et al., 2009; Yaalon and Ganor, 1979).
There are three types of aerosols present today in the atmosphere over the region. Two of these, desert and marine, are natural; the third type is of modern anthropogenic aerosols. Regional wind-blown dust finds its source in the deserts of Libya, Egypt, Sinai, westward (Yaalon and Ganor, 1979) and to a much lesser extent in Saudi Arabia (Ganor et al., 1991). The mineral composition of the dust from both regions is similar, except for the clay mineral composition. The dust is composed of mineral grains including quartz, calcite, dolomite, feldspar, halite, gypsum, and clay minerals (Ganor et al., 2009, Fig. 2A-D). The feldspar content is generally small, comprising approximately 3 to 5 %. However, locally where basalts are exposed, such as along the Rift Valley (Lake Kinneret, Golan, and Dead Sea stations; Ganor et al., 2009, Fig. 1) the amount of feldspar increases and can become the dominant mineral component (Ganor et al., 1991). Locally, apatite (1 to 5%) has been recovered from dust over the Negev Desert (Singer et al., 2003). Phosphate has been found in dust in the vicinity of Haifa as a minor component (Ganor et al., 1998), the derivation of which is most probably from a local phosphor-gypsum plant, and in the central Negev from exposures of phosphate formations and industrial plants (Singer et al., 2003). These two desert-derived dust sources are similar in composition (enriched with calcium, chlorine, sulfur and phosphate), grain size, morphology, and mineralogy (Ganor, 1975; Ganor et al., 1991). The primary Saharan Desert source contains a clay mineral mixture composed of kaolinite, illite, smectite and mixed-layer clays whereas the dust derived from the deserts to the south (Saudi Arabia) is composed of palygorskite, kaolinite, and some mica (Yaalon and Ganor, 1979). Natural dusts have beneficial affects upon the soils, enriching them in nutrients such as K, P, S, NH4 and organic material (Herut and Krom, 1996). Marine aerosols derived from Mediterranean Sea spray constitute up to 3 % of the dust composition (Ganor, 1975). As these are generally soluble salts such as halite, they would tend not to be preserved within a patina.
Modern industrial-related aerosols
Modern anthropogenic aerosols (the third type) such as fly ash are being released from power plants, vehicle exhaust, industrial plants, (Ganor et al., 2009, Fig. 2E,H and I) agricultural emissions, and heating units (Levin and Lindberg, 1979). Urban dusts have been studied for their chemical composition in Tel-Aviv (Donagi et al., 1979); Jerusalem (Malenky et al., 1983) and Beersheva (Kushekevsky et al., 1983). The anthropogenic component is often characterized by the presence of potential biologically active heavy metals, particularly lead, vanadium, nickel, chromium, copper, and zinc. Ganor et al. (1991) found that modern aerosols are generally richer in lead and brome due to the use of leaded gasoline, which is now being eliminated in commercial gasoline. Vanadium and nickel are elemental components of the heavy fraction of fuel oil used in petroleum-based power plants (Ganor et al., 1998) located in Tel Aviv and Haifa, and are chemical characteristics of aerosols that they emit. The Ashdod and Hadera power stations are coal-based.
In Biblical times the majority of particles settling on the ground and other surfaces were natural particles identified as carbonate, quartz, clay, and some feldspar. In recent centuries, however, industry has contributed a significant amount of anthropogenic contamination. These man-made particles can be used to distinguish authentic ancient artifacts from attempted modern forgeries. Fibrous particles in general are characteristic of anthropogenic contaminants introduced in modern times through industrial processes. Examples of industrial particles are asbestos fibers that detach from the asbestos cement blocks widely used in building since 1952 (Ganor et al., 2009, Fig. 2F). Other fibrous materials include basalt, glass, and carbon fibers, all of which are used as insulating materials and represent recent particulates introduced into the atmosphere as dust. Basalt is used in the Kingdom of Jordan as raw material for the industrial production of fibrous rock-wool. Clumps of small metals spheres composed of iron and copper, along with a variety of ancillary heavy metals, are modern contaminants arising from welding and the metallurgical industry.
The introduction of coal power stations has resulted in the release of fine particles of coal and fly ash. These dust particles are identifiable by their spherical shape and small size (generally <1 μm; Ganor et al., 2009, Figs. 2H and I). Black particles of soot released from oil-based power plants contain carbon, nickel, vanadium, zinc, titanium and copper. With the upsurge in construction, the building industry resorted to fabricating white bricks made of pumice, amorphous silica, and tobermorite called Autoclaved Aerated Concrete (AAC). Aerosols resulting from the abrasion of these materials also contribute to the make-up of modern dust. Fine-grained particles of poorly defined morphology but rich in carbon, lead, and brome originate from the exhaust fumes of diesel and gasoline powered vehicles (Ganor et al., 2009, Fig. 2F). These represent modern contributions to airborne dust especially over urban areas. Gunpowder residue identified by its morphology, size (1-2 μm), and three typical elements, namely, antimony, barium, and lead, is likewise a relatively modern contribution to the composition of ambient dust.
Modern dust over Israel contains pollen particles and spores from agriculture and the ornamental flower industry. Monitoring of the range of pollen particles has been carried out in Jerusalem and Tel-Aviv (Horowitz et al., 1975). In the arboreal fraction of modern pollen five tree types are overwhelmingly dominant: Quercus spp., Olea europaea (Ganor et al., 2009, Fig. 2J), Eucalyptus spp., Cupressus sempervirens and Pinus halepensis. The other contributors occur infrequently and sporadically in minor amounts. All of the pollen observed and collected represents plants growing within Israel and the adjacent regions today. One exception is the Eucalyptus spp. for it is clearly not indigenous, being a modern import from Australia since the late 1800s. Likewise, pollen from fruits and shrubs that have been recently introduced can be used to differentiate recent from ancient artifacts. For example, the tomato, potato, egg plant and corn, all dietary staples today, are post-Columbus, coming from the Americas. Even the Sabra cactus was introduced from the Americas. Likewise, the common yellow flowering wild mustard (Eruca sativa) is believed to have been introduced into the region by the Crusaders. There are other non-indigenous plants that can contribute to the local pollen spectrum and their presence within a patina offers another potential key for use in authenticating and dating an artifact.
Calcareous microfossils and nannoplankton, primarily foraminifera and coccolithophorids, are other elements that are commonly found in airborne dust (Ganor et. al., 2009, Fig. 3A-J). At El-Arish, in northern Sinai, fragments of modern land snail shells are a characteristic fraction within the regional dust components (Ganor, 1975). The microfossils found in the trapped dust range in age from Cretaceous (145.5 - 65.5 million years) to Palaeogene (65.5-23 million years). Thus, they are similar in age to the marine carbonate rocks that are widely exposed over most of Israel. The microfossils were studied from dust collected from Haifa, Jerusalem, and Tel-Aviv by Dr. Shimon Moshkovitz (personal communication) of the Geological Survey of Israel (Table 1, Ganor et al., 2009) and are extremely well-preserved, generally with intact tests (shells). The fact that the foraminiferal chambers are empty enables them to easily become airborne (Ganor et al., 2009, Fig. 3, C, D). These microfossils should be as plentiful in the historical past as they are today. These marine carbonate microfossils were indeed found within the patinas of the Jehoash inscription, the James ossuary, and the ivory pomegranate may be an indication of their authenticity. Microfossils can be used to provenance inorganic artifacts (Quinn, 2008) and their absence within a patina purportedly coming from the Jerusalem area would be suspicious since the entire city is situated upon marine Cretaceous carbonates.
The annual amount of atmospheric dust that settles out over Israel decreases from south to north, averaging 200 tons/km2 to 30 tons/km2, respectively (Ganor and Mamane, 1982). During dust storms the amount of dust that settles out over Jerusalem, situated on the desert boundary, ranges from 0.1 to 1.1 g/m2/hr, a significant amount. The thickness of loess that has accumulated in Beer Sheva Valley since the start of the Quaternary is calculated at 13.5 m (Yaalon and Ganor, 1979). The dust that is removed from the atmosphere during rainfall is different in size distribution from the material of dry dust storms. During dust storms, the sediment that is deposited exhibits a bimodal grain size distribution. One mode represents <20-60 μm silt and the other <2 μm clay. Rainfall deposits smaller-sized material in a unimodal distribution. The clay-sized component of rain is 50%-65%, compared to only 10-20% from dry deposition. Clay is often attached to the larger silt-sized particles; however, not all clay-size particles are clay minerals.
Dust is an important component of soils in a tel (artificial mound) environment and was ubiquitous at ancient sites in the Holy Land. Patinas that developed on artifacts over many years accreted elements from the surroundings that existed within those dust-rich soils. The wind patterns apparently were similar during the last millennia in Israel and Sinai (Enzel et al., 2007). Thus the dust contained in patinas of true artifacts can be differentiated from patinas containing modern dust contributions. The analysis of dust components in a patina will assist in validating an artifact’s antiquity whose authenticity may have been called into question.
The microfossils derived from the weathering of the Cretaceous to Palaeogene exposed rocks are deposited by wind. Indeed well-preserved marine carbonate microfossils, such as Cretaceous to Eocene foraminifera and nannoplankton, occur in abundance in everyday dust in Jerusalem (Ehrenberg, 1860; Ganor, 1975 Ganor, et al. 2007, 2009) as well as in the local soils.
During the past several years at least three artifacts of historical importance have been labeled modern forgeries because it was contended that their patinas contained alien material. It should be pointed out that in all three cases a principal argument against authenticity of artifacts from Jerusalem was the presence of marine microfossils within their patinas. An example of this problem can be found in the study of the patina of the tablet with the inscription referring to King Jehoash (Ilani et al., 2002, 2008). Though, its provenance is not readily verifiable, its historical significance is potentially of tremendous importance. One of the arguments that had been used against its authenticity was the finding of Cretaceous-age foraminifera in the patina (Goren et al., 2004). Likewise, the presence of marine nannoplankton (specifically coccolithophorids) of Cretaceous age incorporated into the patina of the ossuary that was related to James with the inscription “Yaakov Son of Yosef Brother of Jesus” also from the Jerusalem area, was likewise construed as proof (among other arguments) of its being a modern fraud (Ayalon et al., 2004), though these artifacts lack any representatives of modern dust contaminants within their patinas. In the third example, an inscribed ivory artifact in the shape of a pomegranate was also considered to be a fake because it too contained Cretaceous marine nannoplankton within its patina (Goren et al., 2005). Other epigraphical and archaeometric considerations that strengthen the pomegranate authenticity are discussed in Lemaire (2006) and Rosenfeld and Ilani, (2006). Yet, as has been noted, these Cretaceous foraminifera and coccolithophorids are natural components particular to, and common in Jerusalem dust; both today’s dust as well as dust from the historical past. Their presence in the patina is entirely natural, coming from the physical erosion of the extensive natural exposures of Cretaceous marine limestones and chalks. Indeed, their absence, on the other hand, within an accreted patina from Jerusalem, should be construed as suspicious. Modern contaminants, as mentioned above, have not been encountered within the patinas of these three artifacts.
Other particles that were found preserved in the ancient patina of the Jehoash Inscription tablet are carbon ash and gold globules associated with burning. These carbon ash particles dated by radiocarbon to 2250 +- 40 years BP may indicate the authenticity of this unprovenanced artifact
(Ilani et al., 2002, Figs. 5 and 6; Ilani et al., 2008, Figs. 6 and 7; Ganor et al., 2009, Fig. 2J ).
The components of dust are related to the geological and floral environment. The dust from that environment can be trapped and preserved within the patina of an artifact, preserving its geological and time signature. Dust, which is ubiquitous in the Levant, can be implanted and preserved within an accreting patina. Modern-day dusts in urban as well as agricultural regions within Israel differ in composition from their historical counterparts. Ambient dust from other geographical regions contains characteristic components that can be used to reveal the area of origin. Archaeological materials as well as blatant forgeries are all exposed to the local environment, be it that of a tel, a cave, soils, or the ambient air of a laboratory. The dust in the patina of an ancient artifact and that of a forgery may be significantly different, especially if the forgery was carried out in a geographical region different from the one that it purports to represent. Therefore, it is proposed that when the validity of potentially important artifacts is called into question, the dust preserved in the accrued surface patina be studied along with the other ancillary methods (within the inner layer of the patina) in the process of archaeological authentication. Additional research is needed to determine how widely an analysis of dust in patinas might be of use, geographically or temporally.
We do not see any limitation to this technique other than that there is no ambient dust in a particular region; however, this is not a problem in the Middle East. One potential problem is misidentification of the inclusions, whether they are fossils or anthropogenic particles. Although the debate on the authenticity of the Jehoash inscription tablet, the James ossuary, and the ivory pomegranate is ongoing at present, the natural dust components occurring within their patinas are good examples to illustrate how the examination of included dust can help clarify and validate artifact authenticity.
We thank Dr. H.A. Foner, Geological Survey of Israel, for his helpful comments and critical review. Dr. T. Minster, Mrs. Rimona Siman-Tov, Mr. M. Dvorachek. all of the Geological Survey of Israel, provided technical assistance.
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