Mineral: Galena
Chemistry: PbS
Size: 35 mm
Owner: Malcolm Southwood
Photographer: Malcolm Southwood

Despite its abundance as a major component of the sulphide mineralisation at Tsumeb, well-formed crystals of galena are somewhat uncommon.  The majority of such crystals, however, show prominent and characteristic striations on at least some of the crystal faces.

This specimen is quite unusual, in that the galena crystal is "hoppered", with a stepped, hollowed habit resulting from skeletal growth (see Photograph 2).  The outer faces of the main crystal, however, provide a very good example of the striations noted above (see Photograph 1). There are, in fact, two intersecting sets of striations visible here. Superficially, at least, these resemble the lamellar twinning described by Ramdohr (1980), which may have developed as a result of mechanical deformation.