kaolinite

Kaolinite is a widely distributed mineral at Tsumeb although for the most part it is inconspicuous. It occurs mainly as an alteration product in shear zones and in the feldspathic sandstone (Hughes 1987) but is also found sparingly in sulphide and oxidised ores.

Pinch and Wilson (1977) noted the occurrence of kaolinite as "… white chalky masses to several cm in size".

Keller (1984) commented on the rare occurrence of kaolinite (also montmorillonite and phlogopite) as secondary minerals in the supergene environment. Fraipontite shares a similar habit and mode of occurrence.

Lombaard et al. (1986) list kaolinite as a very common mineral at Tsumeb.

Hughes (1987) noted the occurrence of kaolinite in shear zones at the margin of the ore pipe. The fill in these shear zones had previously been interpreted as talc by Söhnge (1964) but XRD analysis of sheared material from W120/W136 on 31 Level (at the southwestern margin of the deposit) showed that it consists of quartz, illite and minor kaolinite with no indication of talc. Hughes (1987) also noted the occurrence of kaolinite in sheared sandstone and pyrite-sericite-kaolinite alteration elsewhere in the feldspathic sandstone.

Kaolinite is a named component of the type assemblage for gerdtremmelite (Schmetzer and Medenbach 1985), in association with betpakdalite, hematite, powellite, quartz and scorodite.

A specimen in the Feinglos Collection has minute colourless platy crystals of kaolinite (XRD confirmed) on anglesite. This specimen is now in the collection at Harvard University (MGMH 2022.4.3312T).

A specimen in the Southwood Collection (MS2014.047) comprises a well-formed wulfenite crystal on a galena-rich matrix, with a pearly white crust of kaolinite mixed with kegelite (both XRD confirmed).

albite; azurite; betpakdalite-CaCa (?); cerussite; galena; gerdtremmelite; hematite; kegelite; leadhillite; microcline; muscovite; orthoclase; powellite; pyrite; quartz; scorodite; wulfenite; zharchikhite