Porcelain from Sao Joao and other shipwrecks.

Nearly 500 years after the Sao Joao was wrecked (1552), pieces of porcelain continue to be found on beaches near Port Edward, Natal - the location of the wreck according to current research.

In fact, typical blue-and-white Chinese porcelain shards occur at 10 locations along this south-eastern coast of South Africa. The wrecks believed to be associated with these sites are:  Sao Joao 1552; Sao Bento 1554, Sao Thome 1589, Santo Alberto 1593, Sao Joao Baptista 1622, Sao Goncalo 1630, Nossa Senhore de Belem 1635 and Nossa Senhore de Atalaia do Piheiro 1647.

Porcelain found on beach near Port Edward,
in all likelihood from the Sao Joao.

The porcelain washed up in the Port Edward vicinity is usually in small pieces making identifying marks - for dating purposes - difficult to find. According to experts, however, the porcelain from the Sao Joao dates to the Jiajing period, 1522-1566: (Ming dynasty).

An interesting factor when it comes to dating porcelain shards from shipwrecks is that porcelain was regularly in use as ballast i.e. material laid down in the hold of a vessel to provide stability. Porcelain was also carried for the export trade market: the Portuguese were the first seafaring people to reach China via the Cape of Good Hope. In the early 16th c they carried the first consignment of china wares via the Cape to Europe.

Further reading: 
Turner, M: Shipwrecks & Salvage in South Africa
Vieira de Castro, F: The Pepper Wreck: A Portuguese Indiaman at the Mouth of the Tagus River

In contrast to the other major European imports of the time (for example textiles or spices), ceramics are able to withstand exposure to water, thus making it the ideal merchandise to serve as ballast cargo in the great ships. (Vieira de Castro, F: The Pepper Wreck)