tropical soils. Examples observed in later times can nonetheless suggest a range of possibilities. André Álvares de Almada, a Luso-African merchant from the Cape Verde Islands who traveled and lived at times on the Upper Guinea Coast in the second half of the sixteenth century, described a form of locally made bar iron being traded up the Gambia River at that time. He took care to note that it was the product of local mining and smelting operations, and he described the physical bars as measuring a hand-span long, three fingers wide at one end, and two fingers wide at the other. Among the dealers in this bar iron, Luso-African merchants were especially keen to have it for their trading voyages to the bays south of the Gambia River around Cacheu and Bissau.10 High demand for bar iron in these latter two locales, together with the description of its form and dimensions, suggest that this particular bar iron unit was a semifinished quantity of the metal based either on agricultural tools, such as a hatchet or hoe blade, or on a personal weapon such as a knife blade.
A later example of bar iron, the famous so-called Kissi pennies of the nineteenth and twentieth centuries, was a much smaller currency form most likely based on a generic arrowhead. These particular units circulated among a number of different language groups in the forest and savanna areas of modern Sierra Leone, northern Liberia, and southern Guinea-Conakry.11 That there were so many specific kinds of useful iron products meant that blacksmiths in different locales had the option of shaping particular bar iron currency units, from small ones to large, both “trademarking” their own products and serving a complex consumer market made up of distinctive and various local needs and preferences.
However, several factors set limits on iron smelting that made it difficult to generate a sustained high-volume production of locally made iron. The hardwood trees preferred for making charcoal fuel became scarce at times through overexploitation, for example, especially in locales where smelters regularly operated large shaft furnaces in smelts that lasted several days or up to a week at a time. Other types of West African smelting furnaces were smaller and so required less charcoal, but they were able to produce only modest amounts of workable iron per smelt. Additional limitations came from the restriction of smelting to the dry season and from the control master smelters exerted over access to iron smelting technology and the specialized skills for carrying it out. Taking these limitations together, it is likely that blacksmiths’ potential demand for supplies of smelted iron and consumers’ demand for their finished iron products were not easily or consistently met. This general fluctuating scarcity helps explain in part why West Africans placed such a relatively high value on iron and why, in turn, European merchants in the era of Atlantic trade encountered such robust markets for their overseas bar iron, especially along the Upper Guinea Coast.
West Africa’s other major historical change between the eleventh and fifteenth centuries—a steady growth in its population of Muslims—led to an increasing influence of Islam in its economies, cultures, and urban life. Al-Bakri, in a manuscript completed in Andalusia in 1068, provided general descriptions of what he called the kingdoms of Gao on the middle Niger River, Takrur in the valley of the Senegal, and Ghana between them on the edge of the desert. He drew his views of these kingdoms from knowledge and direct observations of Muslim travelers and traders as well as from the hearsay they had picked up south of the desert. Taking care to point out the towns in which there were mosques and resident Muslims, he also noted the persistence of polytheistic belief and customs in some locales, including among the leaders of important kingdoms such as Ghana. Other telling details—about the gold trade, the significant numbers of Muslim scholars and legal experts in Ghana, and the prominent positions of Muslims as advisors to its king—would have sent a welcome signal to his readers that their faith was on the rise south of the Sahara.12 And this was indeed the case.
Eighty-six years later the Moroccan geographer al-Idrisi provided valuable additions to what was already known about The Land of the Black People, including news that Ghana’s king was now a practicing Muslim. He also passed on general information about the alluvial goldfields adjacent to the kingdom and the vigorous and lucrative trade in gold northward to the Maghreb, where it was minted into dinar coins. Matters of dress were also of great interest, especially when they indicated that there were peoples south of the Sahara who displayed a Muslim sense of sartorial propriety. Respectable Islamic clothing consisted of waist-wrappers, mantles, tailored shirts, and loose-fitting trousers, made of either local cotton or imported wool or silk.13
Regular extraction of gold from deposits located south of the Sahara helped create an interregional currency zone and an early and important north–south axis of trade out of the goldfields and across the desert to North Africa. Muslim Berber merchants traveling southward from Morocco and Tunisia purchased rock salt that had been mined in Saharan deposits and then cut into standard-sized slabs by slaves from southern non-Muslim regions. They carried their units of rock salt onward to the edge of the desert, where they sold it to specialist long-distance Muslim Juula merchants for an agreed-upon measure of gold. Arabic was the language these merchants had in common, at least for trading purposes. Rock-salt slabs thus entered Juula networks and circulated widely in West Africa as a currency valued either by weight or by linear measure, especially in areas where sea salt was scarce.
The gold dust people exchanged in and around West Africa’s towns and cities came from panning stream beds and surface soil in the resource areas around the headwaters of the Senegal and Gambia Rivers during the dry season, or, in some regions, nuggets were won by mining underground veins. The yields then circulated as a currency in units defined by weight. For measuring out units of gold dust currency, Juula merchants had adopted a special apparatus from the Muslim world via the trans-Saharan trade—a balance scale and a set of weights based on the Islamic ounce and pound. The mithqal, an Islamic unit of weight of about 4.25 grams, the standard weight of a dinar coin, thus became a shared currency value and a major vehicle that enabled and encouraged trade to take place between North and sub-Saharan African economies.14
The Cape Verdean Álvares de Almada recorded his own direct observations of Juula merchants buying gold in a town on the north bank of the upper Gambia River in the second half of the sixteenth century. Traveling overland in heavily guarded caravans, they carried their gold dust in small containers concealed in their clothing for safekeeping. Most of it was in the form of very fine flakes of metal, and Almada deemed it very high in quality, that is, it was not debased by the addition of brass filings or other impurities. He wrote admiringly of the Juulas’ reliability and expertise in trading matters, especially the care they took in the skillfully precise handling of their weights and scales. He described the apparatus and equipment in some detail, noting in particular the accuracy of the balance scale, its elegant construction, and the fine quality of its materials. The weights were made of brass cast in a minutely calibrated range of sizes and shapes, which each merchant stored in the drawers of his leather-bound writing case. Almada’s curiosity was piqued by the fact that when Juula traveled to the resource area, they acquired their gold mostly in exchange for copper bracelets, a transaction that from his perspective would not have been profitable to the suppliers of the gold since they acquired only a base metal in return. Making inquiries into the matter, he came to understand that the Juula were simply responding to the cultural values of peoples in the goldfields who preferred copper ornaments to their gold. No doubt sensing a profitable opportunity, he inquired yet further into exactly how much copper would yield how much gold but found he had reached the limit of what the Juula—surely sensing his avarice—were willing to disclose about their commercial operations.15 Secrecy was one of the ways people protected their trading networks, preferred markets, and most reliable suppliers.
Muslim merchants introduced another currency, cowry shells, from either the Near East or the Indian Ocean basin into West African networks via trans-Saharan trading routes at least as early as the eleventh century. Evidence of this traffic comes from travelers’ accounts collected and written down by al-Bakri, which mentioned cowry imports observed at that time in the vicinity of Gao. Other written sources from the twelfth and thirteenth centuries make additional references to cowries being carried across the Sahara along the western caravan route leading southward from Sijilmasa to Ghana. Archaeological remains of a portion of what was one such caravan offer material corroboration of these rather sparse and meager written sources. Whatever the reason for the demise of part of a caravan, whether it was attacked or wrecked by sandstorms and