Image copyrightOLIVIA ACLANDImage captionArtisanal, or freelance, miners are a common site in Sierra Leone's diamond-rich Kono district
A Christian pastor has discovered one of the world's largest uncut diamonds in Sierra Leone's Kono district.
The diamond, weighing 709 carats, is now locked up in Sierra Leone's central bank in Freetown. It is one of the 20 largest diamonds ever found.
Freelance, or artisanal, miners are common in Sierra Leone's diamond-rich areas, reports the BBC's Umaru Fofana.
But there are questions over whether the community will benefit from the gemstone, he adds.
Pastor Emmanuel Momoh's discovery, which has not yet been valued, is the biggest diamond to be found in Sierra Leone since 1972, when the 969-carat Star of Sierra Leone was dug up.
It is also the 13th largest diamond ever to be found, says Mathew Nyaungwa from Rough and Polished diamond analysts.
Mr Nyaungwa adds that it is difficult to estimate a price as it is "quality not size [that] determines the value of a diamond". Our correspondent says that the discovery may have a blemish.
Last May, diamond-mining firm Lucara sold a 813-carat stone for $63m (£51m) at a closed auction in London.Image copyrightUMARU FOFANAImage captionThe diamond weighs over 709 carats
The diamond was first taken to President Ernest Bai Koroma on Wednesday evening before being locked up.
The president "thanked the [local] chief and his people for not smuggling the diamond out of the country", a statement from the presidency says.
Mr Koroma said that the owners should get "what is due to them" and it should "benefit the country as a whole", it adds.
World's five largest diamonds:Image copyrightAFPImage captionThe Star of Sierra Leone, the world's fourth biggest discovery, was found in 1972
1. Cullinan Diamond, found in South Africa in 1905, weighed 3,107 carats
2. Lesedi La Rona, found in Botswana in 2015, weighed 1,111 carats
3. Excelsior Diamond, found in South Africa in 1893, weighed 995 carats
4. Star of Sierra Leone, found in Sierra Leone in 1972, weighed 969 carats
5. Incomparable Diamond, found in DR Congo in 1984, weighed 890 carats
Source: Mathew Nyaungwa, Rough and Polished
Sierra Leone is well known for its diamond industry but it has had a chequered history.
Diamond sales partly fuelled the country's decade-long civil war when rebel groups exchanged them for weapons.
This aspect of the conflict gained global exposure in the Hollywood film Blood Diamond, starring Leonardo Di Caprio and Djimon Hounsou.
There has been a spate of large diamond finds in recent years at mines in southern Africa, including a 1,109-carat diamond in Botswana in 2015.