After accounting for mining depletion of 30 585 ct during the 2023 calendar year, ASX-listed Lucapa Diamond Company and its partners Endiama and Rosas & Petalas have reported that alluvial exploration activities undertaken during the year increased the Lulo alluvial resource in-situ carats by 48% to 228 400.

The diluted gravel, or ore, volume in the updated Lulo alluvial resource is equivalent to eight years of production at Lulo’s planned mining and processing capacities.

Extensive resource definition work since the last update involved auger drilling and trial mining in the southern mining blocks, as well as gaining additional production data from the active mining blocks.

Even with the increase in mining capacities over the last seven years by alluvial mining company Sociedade Mineira do Lulo (SML), the company notes that this is the sixth consecutive year in which the resource carats have increased.

The updated Lulo alluvial resource was independently estimated and reconciled on a depletion and addition basis to December 31, 2023, by external consultants, Z Star Mineral Resource Consultants of Cape Town, South Africa.

The updated Lulo alluvial resource was estimated after taking into account mining depletion to December 31, 2023, by SML mining operations, during which time 30 585 ct of diamonds were recovered from 625 548 bulk cubic metres of gravel.

The estimate also takes into account the delineation of new or additional resources and improved knowledge of existing resource areas through extensive about 11 000-hole auger drilling and about 960 hole pitting programmes, while diamond sales during 2023 totalled $77.3-million at an average diamond price of $2 700/ct.

The company also notes that diamond valuations have been affected by a softening in diamond prices during 2023. The modelled diamond value has been escalated using a global rough diamond price index provided by GTD Consultants, an independent diamond valuation consultancy, up to December 31, 2023.

The modelled diamond values have decreased by about 5% from $2 000/ct to $1 897/ct on average.

To date, about 200 000 ct of diamonds have been recovered on the Lulo concession and sold by SML for about $426-million, at an average price of $2 122/ct.

The total diluted volume of gravel, or ore, available for mining in the updated Lulo Alluvial Resource increased by 90% to 5.02-million cubic metres.

The resource grade in the updated estimate has dropped to 4.55 carats per hundred cubic metres (cphm³) from 5.82 cphm³ in 2022.