
Image Credit: Malcolm Southwood

Image Credit: Malcolm Southwood

Image Credit: Malcolm Southwood



Specimen Title
Malachite after azurite (w. twinned crystal)
Principal Mineral
Precursor Mineral
Size
Cabinet; 51mm
Location in the Mine
First oxidation zone
Provenance
Von Karabacek, H.
Collection
MGMH; 93573
Entry Number
Specimen; TSNB711
Description
An intergrown group of bladed crystals of azurite (to 18 mm), completely replaced by velvety dark green malachite. The two largest crystals are conjoined with an angle that is consistent with twinning on [-102] (Pete Richards, pers.comm. to M. Southwood 2016; exhibits 1 and 2). The pseudomorphs rest on a crust of massive azurite with malachite and a second generation (?) of smaller (and unaltered) prismatic azurite crystals (to 6 mm) has formed at the base of the pseudomorphs.
The specimen was number 4074 in the collection of Austrian industrialist Hans von Karabacek, part of who’s collection was purchased for Harvard University in 1935. The specimen is therefore unequivocally from the first oxidation zone. Von Karabacek’s label (Exhibit 3) indicates that he recognised the presence of twinning ("Zwilling") on this specimen.