La Paz is the capital of the Mexican state of Baja California Sur, situated on the Bahia de La Paz on the western shore of the Gulf of California. From the early sixteenth century to the early twentieth, the bay and the wider Gulf of California (also known as the Sea of Cortez) were among the most productive natural-pearl fisheries in the world. The pearls produced from these waters, principally from the Pinctada mazatlanica oyster (called concha nacar or madre perla locally) and the smaller Pteria sterna, were prized throughout the Spanish empire for their distinctive overtones, dark body colours and exceptional iridescence, and supplied the great pearl jewels of the Habsburg and Bourbon courts.

Historical pearling

The first European pearl harvests from the Gulf of California were recorded in 1533 with the voyage of Hernan Cortes's deputy, who reached the area now known as La Paz. The Spanish Crown formalised pearl tribute and royalties in the sixteenth century, and the pearl industry of the Gulf of California became one of the most important sources of pearls for European markets, second only at certain periods to the Persian Gulf. The fishery operated through indigenous and African-descended divers, working from small craft, with peak production in the seventeenth and eighteenth centuries. The pearls characteristically displayed dark grey, gunmetal, bronze and aubergine body colours with strong rose and green orient, and large baroque pearls of great size were not uncommon.

The Pteria sterna pearl

Of particular interest to the modern gem and pearl historian is the Pteria sterna pearl, sometimes called the 'rainbow-lipped pearl oyster'. Pearls from this species are notable for their exceptionally strong rose and peacock-green orient over a dark body, an effect now considered diagnostic of Sea of Cortez material. Several of the most famous pearls of the early modern period, including the so-called La Pelegrina associated with the Spanish royal collection, are believed by some scholars to have originated in these waters, although the documentation is contested and competing attributions to Persian Gulf or Venezuelan sources also exist.

Decline and the twentieth century

By the mid-nineteenth century the natural pearl fishery had begun to decline through overharvesting. The Mexican Revolution and political instability of the early twentieth century further disrupted the industry, and a disease outbreak in the 1930s and 1940s effectively ended commercial natural-pearl harvesting. In 1939 the Mexican government banned natural pearl fishing in the Gulf of California, and the ban remains in force today. For approximately half a century thereafter the region produced no pearls of commercial significance.

The cultured pearl revival

Beginning in the 1990s, a small number of cultured-pearl operations have been established in the Gulf of California, working principally with Pteria sterna in farms based at Bacochibampo Bay near Guaymas (Sonora) and at Punta Penasco. The cultured Sea of Cortez pearl, produced under controlled conditions and grafted with shell-bead nuclei in the standard manner, displays the same characteristic rainbow orient over a dark body as the historical natural pearls. Production volumes are very small relative to South Sea, Akoya or Tahitian operations, and the pearls are positioned as a connoisseur category rather than a mainstream cultured-pearl line. The CIBJO Pearl Book recognises Sea of Cortez pearls as a legitimate origin category.

Position today

For the modern jewellery historian and dealer, La Paz and the Gulf of California are best understood as a closed historical chapter (natural pearls, sixteenth to twentieth centuries) overlaid by a small contemporary cultured-pearl chapter (1990s onward, principally Pteria sterna). Antique jewels documented as containing Gulf of California pearls are of considerable interest in the auction market, and the modern cultured material has carved out a niche among collectors who appreciate the distinctive rainbow orient. The natural pearl fishery itself remains closed and is not expected to reopen.