State-owned Angop news agency reports that an Angolan citizen and a foreign national had since been arrested.
No further information was given concerning the source of the diamond or its value.
Angolan police recently seized several equipment used in illegal diamond mining in the eastern Lunda Sul province.
They detained 41 illegal diamond miners in the Samusseleca, Saurimo municipality.
Angola also reported in July that it seized 462 diamonds in May and June in Lunda-Norte Province.
Of the diamonds seized, 200 (46, 8 carats) were valued at $9 million, while the value of the other 262 stones was yet to be established.
Operation transparency was launched in December 2018 to combat illegal diamond mining, illegal immigration, administrative infractions, among other things.
More than 6500 diamonds were seized in 2019 under the operation.
At least 19 vehicles and $275,000 were also confiscated while 147,379 foreign citizens were deported for illegal immigration.
Mathew Nyaungwa, Editor in Chief of the African Bureau, Rough&Polished