Bonaparte Diamond Mines (ASX: BON) and Diamond Fields International Ltd (TSX: DFI) jointly announced today that the current phase of joint mining on the Dias Reef area was concluded.

While not categorically stating this would end the relationship Bonaparte's managing director Michael Woodborne said the economic return to date for the partnership does not warrant moving into the next phase of joint operations.

This was despite record recent sale prices, recent vessel operating improvements, though all this was counter-weighed by increased fuel costs and other operational supply issues.

Remaining resources in the joint operations area will be available for future mining should the economics warrant, he said.

Bonaparte recently reported that since mining began on the marine licence in late January 2007 total production to March 2008 stood at 68,047 diamonds weighing 27,793 cts, with an average stone size of 0.47 cts. Total diamond sales for the operating phase, up to April 7, totalled $US5,833,963.

Bonaparte also announced today that its marine focus in Namibia will now be on development of its Meob phosphate project in waters between Walvis Bay and Luderitz.

Woodborne said the exploration target on licence EPL3323 was between 40-50 million tonnes of unconsolidated phosphate sediments with a grade of between 10-15% P205.

A preliminary process flowsheet is being investigated incorporating conventional suction dredging and simple onshore beneficiation, with the objective of producing 3 Mt of enhanced grade (up to 35%) rock phosphate per annum, he said.

The phosphate deposits off Namibia were delineated during regional studies in the 1970s, but have remained undeveloped.

Woodborne said Bonaparte's specialist marine exploration and mining skills placed it in a strong position to develop its marine phosphate projects on the back of the significant upward shift in the phosphate price cycle in 2008.

The company has made application for nine new exclusive exploration licences covering an additional 9,000 square kilometres in areas of phosphate enrichment.

In its March quarter report Bonaparte said it now has a pipeline of South African diamond projects to be brought progressively on stream during 2008 and 2009.

Trial mining and appraisal was being undertaken on the Savanna project in the Kimberley region where two bulk samples of 10,000 tons each were now in progress prior to a decision to purchase a 100% stake in the project for $A1.3 million ($US1.24  M).

Applications have been submitted for alluvial deposits near Bloemhof in the Kimberley region, and the company anticipates gaining an initial licence by June.