Zomba, Malawi

Special thanks to Marcus Grossmann for starting my interest and to Rudolf Cullmann for a steady supply of specimens and informations and a future travel opportunity. Very special thanks also to Alf-Olav Larsen for X-ray identification of some specimens.

The exact locality in this case is not quite assured according to the sparse literature, but at least most of the specimens are coming from Mount Malosa on the Zomba Plateau. The Zomba-Malosa complex is part of the Chilwa alkaline province, where an alkaline volcanim is associated with the east African Rift. The intrusions are plutons of peralkaline granite and syenite and to a lesser degree nepheline syenites and syenites, and also some carbonatites. At Malosa there is a heterogenous mixture of syenite and granite, half of the latter being peralkaline. Acpaitic granite pegmatites are very common here, though they are rather rare in the Zomba region. The alkaline granites are rich in Nb, Ti and Zr as well as in Be, Li, Pb, Mn and Y. Newer specimens, esp. of arfvedsonite and zircon, are said to come from the northern slope of the Zomba plateau, the area where uranium mining is done, too.

One excuse - though there seems to be no eudialyte, it´s alkaline enough for me, and definitely very, very interesting.

Mineral list:
Aegirine
Albite
Annite
Arfvedsonite
Barylite - the world's best
Bastnaesite-(Ce)
Calcite
Cassiterite
Caysichite-(Y) - the world´s best
Chlorite grp.
Elpidit
e - very good !
Epididymite
Epidote
Eudialyte (??? - never seen any)
Eudidymite - probably the world´s best !
Fergusonite-(Y)
Galena

Genthelvite
Goethite
Hematite
Hingganite-(Y)
Illite/Hydrobiotite grp.
Ilmenite
Ilmenorutile

Kainosite
Mangan-Neptunite
Milarite (Y-rich)
Monazite-(Ce ?)
Niobophyllite
Orthoclase-Microcline (not exactly examined)
Parisite-(Ce)
Polycrase-(Y)
Polylithionite
Pyrochlore
Pyrophanite
Quartz
Rhabdophan-(Ce ?)
Riebeckite
Rutile

Scheelite

Siderite

Smektite-grp.

Sphalerite

Synchisite-(Ce) ?
Titanite
Thorite
Xenotime-(Y)
Zircon

In addition the following minerals have been described from the Chilwa Alkaline Province, too, and may be expected at the different Zomba localities (thanks to László Horváth for the information):
Aenigmatite
Annite
Astrophyllite
Catapleiite
Chevkinite
Diopside
Ferri-Katophorite
Fluocerite-(Ce)
Fluoroapatite
Hedenbergite
Hingganite-(Ce)
Lavenite
Magnesio-Arfvedsonite
Nepheline
Pyrite
Richterite
Rosenbuschite
Zirconolite
Zirkelite

8/10/98: I have to thank my friend Alf-Olav Larsen for doing some X-rays on „unknowns“. This has lead to the identification of several new species, which are underlined in the above list. The presence of Y or Ce in the specimens is yet unidentified, however, as Monazite-(Ce) has been described from the Chilwa province, I strongly suppose the same for Mt.Malosa. By the way, monazite seems to be quite common in different habits, sometimes metamict (4/13 „unkowns“). The only REE-carbonates in my material were bastnaesite and parisite, so synchisite seems somewhat doubtful.

2000-8: A new area is being worked now north of the old area on the north slope. There are fantastic parisite-(Ce) crystals (mine is 5cm), good eudidymites and epididymites, pseudomorphs of riebeckite after aegirine, and a lot of siderite. Between the two areas rainfalls have uncovered a vein with crystals to 20 cm of quartz/feldspar pseudomorphs after apatite, covered with epididymite xx and a darkgrey metallic mineral, probably ilmenite/rutile.

2003-12: Alf-Olav Larsen again has done several X-rays of Malosa material. The elpidite confirmed this time really is extremely good. Many of the grey-brown "minerals" quite common on the specimens are mixtures or REE-minerals (rhabdophane and monzite) and chlorite/hydromica/smektite-group minerals, which do not allow for further identification. Probably these are pseudomorphs after unknown (REE- ? )minerals.

Very interestingly the Museum of Natural History and the Institute of Structural Chemistry of Milan University, Milan, Italy are very much involved in the identification of Zomba minerals. However, publications are in German in LAPIS and in Italian in Rivista Mineralogica Italiana so far.


&Suggested reading:
Petersen, O.V., M.Grossmann: Some pegmatite minerals from the Zomba District, Malawi, The Mineralogical Record 25(1994), 1, 29-38

Cairnecross,B., Messner,K, Farquharson,E.: Die Pegmatite des Mount Malosa bei Zomba, Malawi. LAPIS 24(1999), 4, 22-32

Massanek,A.: Neu aus Malawi: Caysichit-(Y), LAPIS 24 (1999), 4, 33

Demartin, F et al.: Neufunde aus den Pegmatiten von Zomba-Malosa, Malawi, LAPIS, 1(2003), 18

Guastoni, A. et al.: Le pegmatiti di Zomba-Malosa (Malawi), Rivista Mineralogica Italiana, 2(2003), 66

Guastoni, A. et al.: Mineralogische Neuigkeiten aus Zomba, Malawi: Genthelvin, Kainosit, Scheelit und Sphalerit. LAPIS, 1(2004), 37

 

Back to main page.