Analysis of the Spillings Hoard
The Spillings Hoard, unearthed in July 1999 on a farm in Gotland, Sweden, remains the largest discovery of Viking Age silver in history. It consists of approximately 67 kilograms of silver, including over 14,000 coins and various pieces of jewelry. A significant portion of this currency consists of Abbasid and Samanid silver dirhams, which traveled thousands of miles from the mints of the Islamic world to the Baltic Sea. Recent scientific advancements have allowed researchers to move beyond traditional typological and metallurgical studies of these coins, employing numismatic palynology to investigate the specific environmental conditions these objects encountered during their long transit across the Eurasian continent.
By analyzing the microscopic pollen grains trapped within the granular patina of the dirhams, scientists have identified distinct botanical signatures that correspond to the flora of the Eurasian Steppe. This research focuses on the presence ofArtemisiaAndPoaceaePollen, taxa that are characteristic of the semi-arid grasslands through which the Volga Trade Route passed. The identification of these grains provides concrete empirical evidence for the movement of silver through the Khazar Khaganate and other intermediary territories between the Caspian Sea and Scandinavia.
What happened
- Discovery and Scale:The Spillings Hoard was found using metal detectors on the Spillings farm in Slite, Gotland; it contained 14,295 Islamic silver coins, illustrating the massive scale of 9th and 10th-century trade.
- Technological Application:Researchers applied numismatic palynology, a specialized discipline that extracts and identifies pollen from the surfaces of historical coins to reconstruct past agricultural and geographical distributions.
- Extraction Method:Scientists used high-purity, deionized water washes and ultrasonic cavitation to dislodge fossilized and desiccated pollen from the bas-relief surfaces and oxidation layers of the silver coins.
- Key Findings:Analysis revealed high concentrations ofArtemisia(sagebrush/wormwood) andPoaceae(grasses), which are not native in such density to the Baltic region but are ubiquitous in the Eurasian Steppe.
- Route Verification:The presence of these specific pollen taxa on coins minted in Samarkand and Baghdad confirms their transit through the Volga Trade Route, specifically through regions controlled by the Khazars.
Background
The Viking Age (c. 793–1066 CE) was characterized by an expansive network of trade that linked the North Atlantic to the Near East. Silver was the primary currency of the Viking economy, and the Islamic dirham was the most stable and available form of bullion during this period. The 'Volga Trade Route' served as the primary eastern artery for this flow of wealth. It originated in the caliphates of the south, passed through the Caspian Sea, ascended the Volga River, and eventually reached the Baltic through the northern waterways of modern-day Russia and Belarus.
The Khazar Khaganate, a Turkic-led multi-ethnic polity, controlled the lower Volga and the northern Caucasus during the peak of this trade. As a major intermediary power, the Khazars facilitated the exchange of northern commodities like furs, slaves, and honey for southern silver and silk. Until recently, the movement of these coins was tracked primarily through archaeological finds and historical accounts such as those by Ibn Fadlan. However, numismatic palynology provides a biological record of the physical environments the coins occupied, filling gaps in the textual record regarding the exact nature of the transit through the steppe environment.
Numismatic Palynology: Methodology and Extraction
The process of numismatic palynology is uniquely rigorous due to the minute quantities of material available on metallic surfaces. Unlike soil samples or peat cores, which offer high concentrations of pollen, coins provide a limited surface area that requires meticulous extraction protocols. Researchers at specialized laboratories use high-purity, deionized water washes to prevent modern contamination. The primary method for dislodging deeply embedded grains is ultrasonic cavitation. This process involves the application of high-frequency sound waves in a liquid bath, creating microscopic bubbles that collapse against the coin’s surface. This mechanical energy effectively loosens pollen trapped within the granular patina formed by centuries of atmospheric oxidation and subterranean burial.
Once the wash is collected, the material undergoes differential centrifugation and density gradient separation. These steps isolate the lightweight organic pollen from heavier mineral particles and metallic residues. To enhance the clarity of the pollen walls for identification, researchers employ polycarbonate filter-based acetolysis. This chemical treatment dissolves the internal cytoplasm of the pollen while preserving the durable outer layer, known as the exine. This preservation is critical for visualizing the ultrastructural details necessary for taxonomic classification.
Microscopic Examination and DIC Imaging
Identification of the recovered pollen requires high-magnification microscopic examination, typically utilizing phase-contrast and differential interference contrast (DIC) microscopy. These techniques are essential for discerning subtle features such as pollen wall stratification, aperture morphology, and exine ornamentation. Precise calibration of objectives allows the palynologist to distinguish between various species ofArtemisiaAnd different genera within thePoaceaeFamily. By mapping the specific morphological traits of the grains found on the Spillings dirhams, researchers can match the assemblage to contemporary flora contemporaneous with the coinage minting and circulation.
The presence ofArtemisiaIs particularly diagnostic. This genus thrives in the dry, saline soils of the Eurasian Steppe and the Central Asian plateaus. Its consistent appearance on coins from the Spillings Hoard suggests that the silver remained in the steppe environment long enough to accumulate significant environmental dust. This accumulation likely occurred during periods of transshipment, market exchanges, or temporary burials in transit through Khazar territories.
Reconstructing the Volga Trade Route
The data derived from the Spillings Hoard allows for a more granular reconstruction of the Volga Trade Route. The dirhams minted in Samarkand, a major hub of the Samanid Empire, show a higher density of Central Asian pollen profiles. These profiles change as the coins progress toward the Baltic. Comparison with contemporary soil strata from archaeological sites in the Khazar capital of Itil and the trading center of Bulghar shows a strong correlation in pollen assemblages. This suggests that the coins were not merely shipped in sealed containers but were exposed to the open air during transactions in these major steppe entrepts.
Furthermore, the absence of certain West European forest pollen on these specific dirhams reinforces the theory that the eastern silver reached Gotland via the Volga rather than through secondary western routes. This methodology allows for the precise dating of trade activity by correlating the pollen assemblages with known climatic shifts and agricultural expansions in the steppe regions during the 9th and 10th centuries.
Archaeological and Geographical Implications
The implications of this research extend beyond the study of Viking trade. Numismatic palynology offers a new tool for verifying trade transit through regions where historical records are sparse. For the Khazar territories, which left behind few internal documents, the biological evidence found on the coins provides a proxy for their environmental and economic history. The reconstruction of trade routes influenced by agricultural products—such as the presence of cereal crop pollen alongside wild steppe species—indicates that the silver moved through active agricultural zones where trading caravans stopped for supplies.
This rigorous methodology also aids in the dating of archaeological strata. In cases where coins are found in disturbed soil, the pollen adhered to the coin itself acts as a 'time capsule' of the environment in which the coin was last handled or stored. This helps archaeologists differentiate between the date of the coin's manufacture and the actual date of its deposition in a hoard. By aligning the numismatic evidence with the phytogeographical distribution of plants in the early Middle Ages, researchers continue to refine the map of the ancient world’s economic interdependencies.
