Lulo hosts a major kimberlite province and extensive diamond-bearing alluvial gravels.

Lulo lies within the ideal tectonic and stratigraphic setting where the Lucapa Graben crosses Angola’s most diamond rich Cuango basin. The Lucapa Graben is the same geological belt hosting most of Angola’s producing kimberlite mines, including neighbouring Catoca, the world’s fourth largest diamond mine.

Lulo hosts 296 kimberlite targets in two separate provinces, of which 96 have been classified as proven and probable kimberlites and four confirmed as diamond-bearing pipes.

Alluvial diamonds
Alluvial diamonds is the term used to describe diamonds that have been eroded from its primary source (ie from a kimberlite or lamproite intrusive host) and over time (millions of years) deposited in a new secondary environment such as gravels in a river bed, or off-shore.

Three different aged gravel horizons within the project area:
• Calonda Formation: a fluvial sedimentary sequence of Late Cretaceous age, largely accumulated as fan deposits and braided stream washes which formed around the time of the kimberlite eruptions in the area. Poorly-sorted diamondbearing basal gravel (0.3 - 4m in thickness) overlain by gritty sands and silts.
• Kalahari Formation: a gravel horizon at or near the base of the Kalahari Formation, largely wind-blown sand unit with fluvial components near the base. The gravel units contain abundant kimberlitic indicator minerals and diamonds.
• Recent River Terraces: significant diamondiferous gravel deposits associated with the current river system.

Alluvial mining and exploration activities at Lulo have until recently been focused primarily on the terrace deposits along a ~50km stretch of the Cacuilo River running through the ~3,000km2 concession, much of which remains untested.

However, through ongoing exploration programs, the Lulo partners recently discovered that in addition to the terraces, the previously-untested flood plains (leziria areas) along the Cacuilo River also host large and premium-quality diamonds.

These flood plains are extensive, highlighting the potential for a significant expansion of diamond resources and mine life at Lulo.

Lucapa and its Angolan partners Endiama and Rosas & Petalas commenced commercial alluvial diamond mining operations at Lulo in January 2015.

Alluvial mining and exploration activities at Lulo have until recently been focused primarily on the terrace deposits along a ~50km stretch of the Cacuilo River running through the ~3,000km2 concession, much of which remains untested.

However, through ongoing exploration programs, the Lulo partners recently discovered that in addition to the terraces, the previously-untested flood plains (leziria areas) along the Cacuilo River also host large and premium-quality diamonds.

A new Volvo and Caterpillar fleet of earthmooving equpment was purchases and arrived on site during 2019, comprising six excavators, eight trucks, two tracked dozers and a wheel dozer.

This additional fleet is part of an expansion program designer to deliver a ~50% increase annulisated in carat production in 2020.

The recovery process involves DMS separation, Xray sorting of the heavy concentrate and hand sorting of the X-ray concentrate.

Samples are processed through a DMS plant. The plant uses a 420mm diameter cyclone and has a nominal head feed treatment rate of 150 tonnes per hour.

The Lulo large diamond recovery circuit, including a TOMRA sorting unit, went into commercial operation in the December 2016 Quarter, processing oversize alluvial gravels at the Lulo Diamond Project in Angola. As part of the new coarse recovery stream at the 150 tonne per hour diamond plant, the XRT technology has provided to recover individual diamonds up to 1,100 carats. The XRT sorting technology is significantly more effective for the recovery of higher quality low-luminescing Type IIa diamonds.

TOMRA XRT technology is used to process material between 18 and 55 mm in size and allows the recovery of diamonds of up to 1,100 ct.