Anjin is a joint venture company between the Zimbabwe Defence Forces (60%), Zimbabwe Mining Development Corporation (10%) and a Chinese investor (30%). Government sources revealed Anjin representatives approached the Ministry of Mines and Mining Development last week seeking new concessions in response to the company’s falling production levels due to depleted diamond resources.

Since their discovery in 2006 alluvial diamond deposits, which are usually found on the surface, have been heavily extracted with huge benefits accruing to diamond mining companies, but revenue generated has declined as the resource gets depleted.

"It now takes the companies more than four tonnes of gravel to get only 15 carats of gems, which clearly shows alluvial diamonds have been depleted,” said a source. “The revenue has tremendously declined by as much as 90% over the past few months.”

Anjin director Retired Brigadier Munyaradzi Machacha yesterday confirmed meeting with the ministry, but said the purpose was to seek permission for further exploration in Chiadzwa.

"Mining is a continuous process of exploration and surveys to discover new deposits,” Machacha said. “We are conducting geological surveys on fresh concessions not because diamonds are running out, but to discover more so that we keep on mining.”

It is estimated that Marange diamonds account for 25% of total world deposits, but another source insisted the figure was an over-estimation based on speculative exploration.

"Exploration that took place and the resultant estimations were based on the activities of artisanal miners, and on projections around alluvial deposits,” said the source.

A local geologist told the Zimbabwe Independent that alluvial gems are usually deposited on the surface and extraction involves digging and sifting through mud, sand and gravel using shovels, sieves or even bare hands.

"Typically, diamonds come from geological rock formations called kimberlites,” said the geologist. “Kimberlite rock formations that contain diamonds are eroded over time by rivers and streams and can deposit diamonds in the sediments carried by those streams further downstream from the original source rocks. These deposits are called alluvial diamond deposits.”

Last week Finance minister Patrick Chinamasa said Treasury had not received any proceeds from diamond revenue in the nine months to September 2013.

He told parliamentarians in Victoria Falls at a 2013 budget review seminar that out of a targeted US$40 million expected from diamond sales, nothing had been received during the period under review.

Last year Chinamasa’s predecessor, Tendai Biti, was forced to slash the country’s national budget to US$3,4 billion from US$4 billion after receiving a mere US$41 million out of a targeted US$600 million expected from diamond sales.