I think that it if Hinduism. Christianity is more known to worship in churches. Hindus typically have several temples for each of their gods/ goddesses. Muslims (Islam) worship in mosques and Jews worship in synagogues, so it is more than likely Hinduism.
The colony became vastly richer due to the diamond deposits. Even locals happened to gain a lot form it and there is a famous example of a woman who was married to a Portuguese official who died wealthy and could buy anything she wanted. Of course, the working conditions were harsh for the workers.
A) the dominant religion there was catholic.