Alum, Silk, and the Slaves of Caffa

Three commodities besides mastic gave Genoese Chios its commercial character, and each has a story.

Alum, first, because it was the industrial foundation of the whole enterprise. The Phocaean mines, taken by Vignoso along with Chios in 1346 and administered by the same Maona, supplied the mordant on which the European cloth industry ran. Alum went by sea from Phocaea to Flanders, to England, to Florence, to Catalonia, and the Maona behaved as monopolists behave: production quotas, price management, and periodic agreements with rival producers to restrict output.

The monopoly was lost before the island was. Old and New Phocaea fell to Mehmed II in 1455. And in 1461 alum was discovered at Tolfa, in the Papal States a short distance from Rome — a discovery which broke the eastern monopoly outright, funded the papacy handsomely for a century, and removed one of the two pillars of Chios's economy at a stroke. After 1461 the island's position rested much more heavily on mastic and on its function as a transit port.

Silk ran through Chios in three distinct ways, and they are frequently confused with one another.

There was transit silk. Raw silk from Persia — the Caspian provinces of Gilan and Shirvan produced the best in the world — went overland to Tabriz and then either north-west to Trebizond or west across Anatolia to Bursa, which by the fifteenth century was the great silk market of the eastern Mediterranean and the place where Persian silk met European money. From Bursa it moved to the coast and out through the Aegean, and Chios was a principal handling point on that leg. The Italian silk-weaving industry — at Lucca, at Venice, at Florence, and not least at Genoa itself, whose velvets were a luxury export across Europe — depended on the supply.

There was Chian silk. The island grew mulberries and raised silkworms. Sericulture is documented under the Genoese and expanded considerably under the Ottomans; Chian raw silk was of respectable quality, and the island also had a textile industry producing worked silks and mixed fabrics for the Levantine market.

And there was silk as a Genoese strategic interest, which is what tied the other two together: a republic whose own manufacturing depended on eastern raw silk had an excellent reason to hold an island in the middle of the supply chain.

Finally, the Black Sea run, which was in bulk terms the largest business the Genoese did in the east. Grain above all — the wheat of the Crimean and Danubian plains, which fed Constantinople and much of the Mediterranean — together with salt fish from the Sea of Azov, wax, hides, and furs.

And slaves. This requires stating plainly rather than in euphemism. Caffa was one of the great slave markets of the medieval world. Captives taken on the steppe — Tatars, Circassians, Russians, Alans, Georgians, Abkhazians — were sold there in large numbers, and went west into Italy and Spain as domestic servants, and south and east to the Mamluk sultanate of Egypt, whose entire ruling military caste was recruited by purchase and whose demand was accordingly enormous and continuous. Genoese ships carried them, and Chios, as the staging point on the route, handled them. The island's notarial records document slave sales, and Chios itself, like every Mediterranean commercial centre of the period, had a domestic slave population of its own.

There is a bleak symmetry in this that the reader may already have noticed. Eighteen hundred years earlier, Theopompus had complained that his own island was the first Greek state to buy barbarians from the Black Sea. The geography that made Chios a slave-trading node in the sixth century BC made it one again in the fourteenth century AD, for the same reason and along the same route.