Mineral: Azurite, Bayldonite
Chemistry: Cu3(CO3)2(OH)2
Size: 110 mm
Owner: Harvard University (A.F. Holden Collection)
Photographer: Malcolm Southwood

Lustrous blue-black crystals of azurite (to 10 mm) on green bayldonite (?) which appears to be pseudomorphous after azurite (?). 

This superb specimen is number 431 in the A.F. Holden collection, which was acquired by Harvard University in 1912.  This dates the specimen to the upper levels of the mine - almost certainly above 6 Level.   A penciled note on the old label suggests that the bayldonite (?) is after anglesite, but such a replacement has not been recorded from Tsumeb. Azurite (?) seems to be a more plausible candidate as the parent mineral. Please note that the bayldonite has not been verified by modern analysis.

(FOV for the close-up photograph is c. 55 mm.)

Courtesy  of  the  Mineralogical  &  Geological  Museum  at  Harvard  University,  Azurite; MGMH  ID# 109777, Tsumeb; Namibia. @ copyright 2012, President and Fellows of Harvard College. All rights reserved.