Swahili patricians, the ruling class of coastal society of mixed African-Asian origin in the ports and islands of East Africa, comprising Sultans, chiefs, government officials, ship owners and wealthy merchant houses, used non-Muslim slaves as domestic servants, sailors, coolies and workers on farms and plantations, even in the interior of modern day Tanzania around trading centers such as Tabora, Mwanza on Lake Victoria, and Ujiji and Kigoma on Lake Tanganyika. Swahili craftsmen, artisans and clerks were free Muslim men or Islamized former slaves. The divisions between the different social classes were often not very strict because of intermarriage and social mobility. Seyyid Said, Sultan of Oman an Zanzibar, and his relatives and associates, became so rich because of his clove plantations in Zanzibar employing slave labor that he moved his capital Muscat in Oman to Zanzibar in 1840; thus he became the first of 12 Omani Sultans of Zanzibar.