The Catoca kimberlite pipe and mine, is located 35 km NNE of the city of Saurimo in Lunda Norte Province, NE of Angola, close to the border with the Democratic Republic of Congo and has been the main hardrock producer of diamonds in Angola.
Most of the Angolan diamond resources are concentrated in four kimberlite fields within the Archaean Kasai - Angola craton, namely the Camazambo, Catoca, Camutue and Camatchia fields which contain a total more than 70 kimberlite bodies distributed over a NNE trending interval of around 150 km and a width of up to 40 km, controlled by the NNE trending Lucapa regional fault zone.
The Catoca pipe is a 900 m diameter, weakly eroded diatreme which covers a surface area of 65.7 ha. The intruded country rocks comprise Archaean granite-gneisses and crystalline schists. The pipe is overlain by Palaeogene to Neogene sands of the Kalahari Formation, ranging in thickness from the several to 130 m.
The Catoca pipe includes crater, diatreme and hypabyssal facies kimberlite rocks.
Crater facies volcaniclastic rocks comprise heterolithic breccias, psephitic and psammitic tuffs, alevrites and alevrolites with layered textures and variable amount of kimberlitic material.
Diatreme facies are represented by eruptive kimberlite breccias with brecciated, partly autolithic, with massive groundmass textures. The structure of the rocks is porphyritic and clastoporphyritic. The groundmass is composed by serpentine-carbonate with minor amounts of altered phlogophite, rare perovskite crystals and opaque oxide minerals.
The porphyritic kimberlite with massive textures and microporphyritic structures is described as a hypabyssal facies kimberlite. The porphyritic crystals are pseudomorphed olivine and phlogophite. The groundmass is composed by anhedral and euhedral olivine crystals, which are pseudomorphed to serpentine and a serpentine-carbonate mixture. Minor amounts of the phlogophite, spinel, ilmenite, perovskite and apatite are also present.
The chemical composition of the kimberlitic rocks from the Catoca pipe show significant compositional variation between the different facies.
The diamonds from the Catoca pipe are dominantly octahedral, although transitional and dodecahedral habits and flat faced octahedrons are also found. The primary kimberlite minerals are garnet, ilmenite, chrome-diopside and phlogophite.
The Catoca pipe is the largest producer in Angola with an output of approximately 2.8 million carats in 2002. Total Angolan production for the same year was 5.02 million carats of diamond, much of the balance coming from the extensive alluvial diamond fields in the same province.
The estimated reserve of the Catoca kimberlite in 2002 is reported to be 271 Mt @ 70 carats per hundred tonnes for 189.3 million carats of diamonds.
The mine is operated by Sociedade Miniera de Catoca Ltda. (SMC), a joint venture between Empresa Diamantes de Angola - Endiama (32.8%), Russia's Almazy Rossii-Sakha Joint Stock Company - ALROSA (32.8%), Brazil's Odebrecht Mining Services Inc. (18.4%), and Israel's Lev Leviev (16%).
(Source: Porter GeoConsultncy, http://www.portergeo.com.au/, 2004)
