Afrikaans: Andesitiese basalt van die Hekpoort-formasie in Faerie Glen Natuurreservaat, Pretoria. Perkolerende water het akkresie van 'n sekondêre mineraal in die rotsvesikels, sg. amygdules, ten gevolg gehad. Die vesikels is nagelaat deur opgelosde magmagasse wat na verlaging in lawadruk en -temperatuur opgebruis het. Die rots word dateer na die vroeë Proterozoïkum, sowat 2.22 miljard jaar gelede.
English: Andesitic basalt of the Hekpoort formation in Faerie Glen Nature Reserve, Pretoria. Percolating water caused accretion of a secondary mineral, so-called amygdales, in the rock vesicles. The vesicles were caused by dissolved magma gasses that effervesced from the lava due to decreased pressure and temperature. The rock is dated to the early Proterozoic, some 2.22 billion years ago.
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{{Information |Description ={{en|1=Andesitic basalt of the Hekpoort formation in Faerie Glen Nature Reserve, Pretoria. Some of the rock vesicles are filled in with a secondary mineral, to form amygdales. The vesicles were caused by dissolved gasses...