The Liberian government has lifted a six-year-old moratorium on the mining, sale and export of diamonds, imposed at the height of the civil war.
Efforts are being made to ensure the diamonds are properly certified
The industry came under UN sanctions in 2001, when ex-President Charles Taylor was accused of using the sale proceeds to fund wars in West African nations.
Correspondents say he imposed the moratorium in a bid to show compliance.
The UN lifted sanctions in April, saying the new government had moved to ensure the industry's regulation.
Ellen Johnson-Sirleaf was elected president two years ago after the end of the war. She said her government wanted to use diamonds to fund reconstruction efforts and not conflicts.
Nearly half of the world's diamonds come from west, central and southern Africa.
Tracking the diamonds
"As of Monday people can start applying for mining, selling and broker licences," the deputy minister of Lands, Mines and Energy, Kpandeh Fayia, told the BBC.
The BBC's Jonathan Paye-Layleh in Monrovia says that since the UN's decision, the Liberian government has been putting measures in place to control the industry before lifting its moratorium.
The president opened the first of 10 government-run diamond certification offices in May to ensure rough diamonds mined in Liberia and neighbouring Sierra Leone are properly certified.
The international diamond certification scheme - the Kimberley Process, established in May 2000 - tracks the origin of diamonds on the international market.
In the past, the lucrative trade fuelled conflicts in countries such as Angola, Congo, Sierra Leone and Liberia, as rebel groups fought for control of diamonds and found willing international buyers to finance their activities.