Corruption in the chain artificially raises prices, plumping the pockets of the already rich.
Fierce infighting has erupted within the Richtersveld area's structures over the leadership of a community-owned mine.
The 81 countries taking part in the Kimberley Process have called on the US to follow the EU's lead and lift sanctions on Zimbabwean mines.
President Michel Djotodia has said his country would halt trade in diamonds pending reforms to ensure that they are not used to fund conflicts.
A huge, internally flawless diamond from India's fabled Golconda mines has been sold at auction in Geneva for a record $21.48-million.
Human Rights Watch claims Zimbabwe has broken its promise to halt physical abuse of diamond miners and should have its certification frozen.