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[Duncan Miller]

Blue chalcedony pseudomorphs from Ysterputs, southern Namibia
By Jo Wicht and Duncan Miller

Ysterputs farm in southern Namibia is well known for its blue lace agate, a variety of banded chalcedony and quartz. Less familiar are the relatively scarce specimens of cuboid blue chalcedony pseudomorphs found associated with the blue lace agate deposit. These range in size from about 2 mm to 12 mm across, and form encrustations on substrates of laminated chalcedony and dolomite or calcite. They are visually very similar to published examples from Trestia in Romania, the Alberta Badlands in Canada, and several locations in California in the USA. These are thought to be pseudomorphs after melanophlogite, a cubic silica clathrate. The Namibian examples have been assumed to be after fluorite, but their similarity in appearance and geological setting compared to those from Romania, Canada and the USA lead us to believe they too are after melanophlogite.

[Duncan Miller]

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