THE MINERALS OF THE DEMOCRATIC REPUBLIC OF CONGO

An eminently mining country, the Republic of Congo is the centre of numerous exploitations of most diverse metals in a multitude of mines and quarries. Its soil harbours a wide variety of mineral species with facies of often very high esthetical quality.

The worked deposits are distributed over Precambrian massifs bordering, to the south, east and north-east, a vast sedimentary central basin. Thus, in counterclockwise sense, one encounters successively, from south to north: diamantiferous exploitations of Kasai ( Mbuji-Mayi, Tshikapa ), as well as a few copper deposits ( Tshiniama, Lubi ); the copper-bearing arch of southern Shaba, also rich in cobalt and uranium with the mining centres of Kolwezi ( Cu-Co ), Likasi ( Cu ), Kambove ( Cu-Co ), Shinkolobwe ( U ) and Lubumbashi ( Cu ), not forgetting the mine of Kipushi which yields zinc, copper and germanium. Still in Shaba, when ascending northward, one comes across the tin granite of Mitwaba and the stanniferous pegmatite of Manono. The province of Kivu, enclosing the region of Maniema, is particularly rich in tin deposits ( Kalima ), often accompanied by columbo-tantalite. The pegmatite with beryl, the columbite and uranium of Kobokobo also found here, as well as gold placers of the Mobale river. In the north of the province of Kivu, there are outcrops of carbonatite of Lueshe, rich in pyrochlores, while at the Rwandan border, the region of volcanos contains lavas in which several new silicates have been discovered. In the north of Congo, in the Oriental Province, there are the famous gold exploitations of Kilo-Moto. At the western extremity of the country, to the west of the capital Kinshasa, the Lower Congo encloses a few deposits of zinc and lead vanadates ( Kusu-Senge ), whereas the massif of Niari is the centre of fine examples of mineralizations in copper silicates, mainly, however, on the territory of Congo-Brazzaville.

From a mineralogical point of view and more particularly with regard to the esthetical value of the specimens, the names of deposits and their principal resources in nice minerals are indicated in the following list:

Southern Shaba

- Kabolela: black, shining reniform masses of heterogenite.

- Kakanda: mammillary pseudomalachite, green crystals of libethenite and pink cobaltiferous calcite.

- Kalongwe: copper and uranium deposits offering fine examples of associations of cuprosklodowskite in needles and dark green vandenbrandeite in etcher's prisms.

- Kambove: fibroradiated plancheite in crusts and rosettes and centimetric crystals of carrollite.

- Kamiaba: deposit of pink to brown almandin garnets forming crystalline crusts.

- Kamoto: type locality of kolwezite, double carbonate of copper and cobalt in beige to black nodules. Very rare prismatic and tabular crystals of sea green roubaultite occur in the K.O.V. quarry. The oriental part of this deposit contains an uraniferous mineralization where the new minerals astrocyanite-(Ce), françoisite-(Nd), kamotoite-(Y) and shabaite-(Nd) were discovered, containing also rare earths minerals.

- Kamoya: association of copper silicates, plancheite, shattukite and light-blue masses of ''katangite'' with conchoidal fracture.

- Kasompi: another deposit of rare-earths minerals such as schuilingite-(Nd) and gyisinite-(Nd). We also find arborescent pale-green lodes of glaukosphaerite.

- Kipushi: exceptional association of secondary minerals of zinc, lead and copper, such as smithsonite, hemimorphite, aurichalcite,veszelyite ( bright-blue octahedrons ) and emerald green kipushite. The primary mineralization is rich in germanium with renierite and briartite. Green sphalerite and rhenium molybdenite are also found, as well as gallite. The paragenesis is very close to that of Tsumeb in Namibia.

- Likasi: beside cuprite accompanied by native copper, we find here a fine example of the association of buttgenbachite and connellite in bright-blue acicular prisms, of likasite in blue stacked plates and of sea green gerhardtite.

- Ludjiba: type locality of ludjibaite, a polymorph of pseudomalachite.

- Luishya: kyanite in blue tablets is associated with classical secondary minerals of copper.

- Luiswishi: mineralization with copper and uranium, with, namely, cuprosklodowskite in fibres, vandenbrandeite in crystals in burins and sengierite.

- Mashamba: exceptional red gem cuprite in centimetric crystals, but also testaceous malachite, duhamelite in yellow fibres and an uraniferous association of tyuyamunite and carnotite.

- Mindigi: cobaltiferous deposit of mammillary heterogenite and crystalline varieties with metallic lustre among which the polytype 2H.

- Msesa: shining crystals of green libethenite, crystallized pseudomalachite and light-blue claringbullite of which this is the type locality.

- Musonoi: locality especially famous for its uranium selenites: demesmaekerite, derriksite, guilleminite and marthozite. Also renowned for its cobaltiferous malachites and kolwezite.

- Shamitumba: collecting site of the julienite in blue needles.

- Shangulowe: fine examples of associations of copper silicates ( plancheite-shattuckite ) and presence of barite pseudomorphosed in plancheite and in malachite.

- Shinkolobwe: one of the most famous uranium deposits in the world. It has furnished, namely, the raw material with which the first atomic bombs were made. Tens of new species were discovered here. The mine has been closed in the beginning of the 1960s.

- Star mine ( Lubumbashi ): cornetite in blue rosettes.

- Swambo: prospecting site for uranium rich in yellow squat crystals of soddyite and type locality of swamboite.

- Tantara: site of the very spectacular association of green dioptase and bright-pink cobaltiferous calcite.

Kivu

- Bengo-Biri: wolfram deposit enclosing crystals of ferberite and pseudomorphoses in anthoinite.

- Kobokobo: beryl and columbite pegmatite of which a zone is mineralized in uranium. The latter presents a particular association of uranium and aluminium phosphates rich in new species. They are quoted under the heading dedicated to type species preserved in the Royal Museum of Central Africa, in Tervuren.

- Lueshe: carbonatite characterized by an abundance of pyrochlores, and type locality of lueshite in octahedral crystals.

- Maya-Moto: this deposit contains a rich association of bismuth minerals: native bismuth, bismutite, bismuthinite and bismite.

- Mwenga: auriferous district of the river Mobale which has yielded voluminous nuggets.

- Messaraba-Munkuku: deposit of crystallized cassiterite, which is one of the localities of varlamoffite, yellow and powdery hydrated oxide of tin.

- Volcanos: the volcanic region straddling on the border with Rwanda contains lavas from which several new species have been described: andremeyerite, combeite, götzenite, delhayelite and trikalsilite.

The remaining provinces of Congo do not contain such spectacular associations, with the exception of the rich diamantiferous deposits exploited in the kimberlites, the eluviums and alluviums of the region of Mbuji-Maji ( mainly industrial diamonds ) and the gold mines of the Upper Congo ( Kilo-Moto ).

THE HISTORY OF THE CONGOLESE MINERALOGY

The school of Minralogy of the University of Ghent ( Rijksuniversiteit Gent or R.U.G. ) has been particularly active in the study of Congolese mineralogy, under the inspiring guidance of Alfred Schoep ( 1881-1966 ). Either alone or in collaboration with other researchers, he discovered 14 new , mainly uranium-bearing species, in copper-cobalt- and uranium-bearing deposits of southern Katanga: becquerelite, buttgenbachite, curite, dewindtite, dumontite, ianthinite, julienite, kasolite, likasite, paraschoepite,parsonsite, sklodowskite, soddyite and vandenbrandeite. A hydrated oxide of uranium,schoepite, was dedicated to him in 1923, by Walker. The descriptions made by A. Schoep have appeared many times in the publications of the Academy of Sciences of Paris. The first to apply radiocrystallographic methods in their studies of the material from Congo were two students of A. Schoep, Valère Billiet ( 1903-1945 ) and Adrien Vandendriessche ( 1914-1940 ). Both died prematurely during the Second World War. At the same University of Ghent, Marcel De Leenheer devoted himself, in 1934 and 1935, to the study of hydrated oxides of cobalt, collected in the mines of Katanga and mainly in Mindigi and Shinkolobwe. He has recognized new species such as boodtite, mindigite and trieuite. Discredited by Max Hey in 1962, these species have been subsequently united under a single name of heterogenite. The collection containing A. Schoep's type species was lost during the Second World War, but it is quite impossible to know whether it has been destroyed or scattered. Today, several museums claim the possession of type species having belonged to A. Schoep, but the authenticity of such claims is impossible to ascertain.

At the University of Liège, it is Henri Buttgenbach ( 1874-1964 ) who goes on his first mission to Congo in 1902, assigned by the Special Committee of Katanga to observe the workings of the Tanganyika Concessions. In 1906, he carries out a second mission in the gold district of Kilo-Moto. As from 1911, he is appointed administrator of the " Union Minière du Haut-Katanga " and enters upon the study of minerals of the copper-cobalt- and uranium-bearing deposits. He describes the species cornetite, fourmarierite and cuprosklodowskie, as well as the thoreaulite found in the pegmatite of Manono in North Katanga. He publishes a masterly work on Minerals of Belgium and the Belgian Congo, which is an authority in the field and has been republished many times. His successor, Joseph Mélon ( 1898-1991 ), has contributed to the mineralogy of Congo by describing the sharpite of Shinkolobwe. At present, it is André-Mathieu Fransolet who pursues the African tradition with works on granitic pegmatites. He has discovered, namely, gatumbaite of Rwanda and melonjosephite of Morocco.

Finally, at the University of Louvain ( U.C.L. ), Jacques Thoreau ( 1886-1973 ) describes, in 1932, the saleeite of Shinkolobwe in Shaba, while his successor Jules Moreau acquires fame by his study on the copper-zinc-bearing deposit of Kipushi, which enables him to describe a new germanium mineral, briartite. Later on, Paul Piret, crystallographer at the U.C.L., collaborates with Michel Deliens to describe numerous new minerals from Congo ( see below ).

The geologists working in Congolese mines have also largely contributed to the development of the local mineralogy. Thus, Johannes Franciscus Vaes ( 1902-1978 ) has devoted a particular attention to the study of the minerals coming from deposits of the " Union Minière du Haut-Katanga " . We owe him the discovery and description, between 1947 and 1949, of 8 new species: billietite, masuyite, renierite, richetite, schuilingite-(Nd), sengierite,s tudtite and vandendriesscheite. Two other geologists, Théo Verbeek and Robert Oosterbosch turn to French mineralogists, in collaboration with whom, between 1965 and 1971, they describe the uranium-bearing selenites of Musonoi: demesmaekerite, derriksite, marthozite, ( Cesbron et al ) and guilleminite ( Pierrot et al ). In Kivu, Alexandre Safiannikoff discovers the lueshite ( 1959 ) in the carbonatite of Lueshe, whereas the Finns T. Sahama and K. Hytönen devote themselves to the study of the volcanic lavas of Kivu, where they discover, between 1957 and 1959, combeite, götzenite, delhayelite, kirschteinite and trikalsilite. Still in Kivu, Léopold Van Wambeke studies the pegmatite with columbite and beryl of Kobokobo, which enables him to define the kivuite ( 1958 ) and the eylettersite ( 1972 ). This same author also defines the zairite in Etaetu ( 1975 ).

Between 1923 and the present time, other Belgian or foreign researchers have defined, at given times, one or another mineral species the names of which are mentioned at the end of the article. An important contribution to the systematic mineralogy of Congolese deposits in the recent years is due to the collaboration between Michel Deliens ( Royal Museum of Central Africa, in Tervuren, and later, Royal Belgian Institute of Natural Sciences, in Brussels ) and Paul Piret ( Catholic University of Louvain ). These authors have devoted themselves to the study of the copper-cobalt- and uranium-bearing secondary mineral associations of southern Shaba, as well as to the analysis of uranium-bearing mineralizations associated to the granitic pegmatite with beryl and columbite of Kobokobo in Kivu. In Shaba, seven new species have been discovered in uraniferous deposits of Shinkolobwe and Swambo: bijvoetite-(Y), lepersonnite-(Gd), metastudtite, oursinite, sayrite, swamboite and urancalcarite. Four uranium minerals including rare earths come from the mine of Eastern Kamoto: astrocyanite-(Ce), françoisite-(Nd), kamotoite-(Y) and shabaite-(Nd) and five copper- and/or cobalt-bearing species have been described in different deposits: kipushite ( Kipushi ), comblainite ( Shinkolobwe ), heterogenite-2H ( Mindigi ), kolwezite ( Musonoi ) and ludjibaite ( Ludjiba ). Eleven secondary phosphates of uranium and of different cations constitute an original association conspicuous in the pegmatite of Kobokobo: althupite, kamitugaite, metavanmeersscheite, moreauite, mundite, phuralumite, ranunculite, threadgoldite, triangulite, upalite and vanmeersscheite. The latter species, discovered in Shaba in 1996, is the piretite of Shinkolobwe, described by Michel Deliens and Renaud Vochten ( Rijksuniversitair Centrum Antwerpen ).

EXHIBITIONS OF CONGOLESE MINERALS IN BELGIUM

- In spite of the wealth of Congolese minerals and the multitude of samples of excellent quality provided by mining companies and collected either during scientific missions or bought on the spot by travellers, few minerals are offered to the view of amateurs in Belgian public collections.

- In the Royal Museum of Central Africa in Tervuren, a small room is devoted to mineralogy, where a few typical deposits are illustrated: gold of Kilo-Moto ( Oriental Province ), diamonds from Kasai, copper and zinc of Kipushi ( Shaba ), rare copper minerals of Shaba and secondary uranium minerals of Shinkolobwe. This Museum has a very full mineralogical collection including species originating from most of the deposits which have been, or still are, exploited in Congo. This collection is preserved in a repository accessible to specialists only.

- The Royal Belgium Institute of Natural Sciences in Brussels presents a more extended exhibition of minerals, elaborated according to three main axes: the mode of formation and the physical and crystallographic properties of the minerals, the systematics based on the chemical composition ( about one thousand of species are represented ) and, finally, the illustration of the main mineral deposits in Belgium. Congolese minerals are shown only incidentally in some show-cases devoted to the systematics.

- The Belgian Universities with a department of geology, at the present time no longer have real mineralogical museums. Only a few specimens are accessible on didactic premises exclusively, or decorating the corridors of some faculties. The former museums of the Universities of Brussels, Ghent, Liège or Louvain were suppressed after the concerned faculties had moved to new campuses. The type samples appearing in some collections have been partly transferred to the Royal Institute of Natural Sciences.

- As a result of high prices of good-quality samples, and seeing the financial restrictions imposed on public institutions, all spectacular mineral specimens collected today in Congolese mines ( or elsewhere ), usually end up in private collections inaccessible to the general public, and their inventory is difficult to make. They can occasionally be seen at one or another temporary exhibition.

Ninety-two minerals have been described for the first time in Congo. Among these, fifty-four are represented by a holotype sample ( i.e. the specimen used for the original description ) and whose repository is quite certain. Thirty-eight of them are included in four Belgian public collections:

- the Royal Belgian Institute of Natural Sciences ( Brussels ): luberoite, ludjibaite, shabaite-(Nd), françoisite-(Nd), and piretite;

-The Royal Museum of Central Africa ( Tervuren ): althupite, astrocyanite-(Ce), bijvoetite-(Nd), comblainite, heterogenite-2H, kamitugaite, kamotoite-(Y), kipushite, kolwezite, lepersonnite-(Gd), lueshite, metasudtite, metavanmeersscheite, moreauite, mundite, oursinite, phuralumite, ranunculite, sayrite, swamboite threadgoldite, triangulite, upalite, urancalcarite, vanmeersscheite, wakefieldite-(Ce), wyartite and zairite;

- the University of Liège: cornetite, cuprosklodowskite, fourmarierite and thoreaulite;

- the University of Louvain-la-Neuve: briartite and saleeite.

Two other holotypes, eylettersite and kivuite, are preserved in the private collection of the discoverer, while 14 other type species belong to collections of various institutions from abroad:

- the Ecole Nationale Supérieure des Mines ( Paris ): guilleminite, oosterboschite and roubaultite;

- the University of Paris VI: demesmaekerite, derriksite and marthozite;

- the Museum of Natural History ( Paris ): wyartite;

- the Technical University of Berlin: gallite;

- the Museum of Natural History of Geneva: gysinite-(Nd);

- the British Museum of Natural History ( London ): claringbullite;

- the National Museum of Natural History ( Washington ): combeite, götzenite, kalipyrochlore and protasite.

Other public collections claim the possession of holotype minerals, but there is no serious guarantee that these are indeed the specimens that have been studied by the discoverer. This is, namely, the case of the original samples of A. Schoep, while it is quite well-known that his study material which had been preserved at the University of Ghent, was lost during the Second World War.

MINERALS DESCRIBED FOR THE FIRST TIME IN CONGO