The micro-sample of metal examined by ICP-MS showed 3.2-4.6 wt% copper, which is associated with copper-tin minerals such as
stannite, [Cu.sub.2]FeSn[S.sub.4], which is found in Cornish tin mines.
The CZTS is quaternary compounds of
stannite structure; its band gap is about 1.50 ev, which is very close to the best band gap required by semiconductor solar cells (1.35 eV).
Tin does not occur naturally by itself, and must be extracted from a base compound, usually cassiterite,
stannite, cylindrite, franckeite, canfieldite, and teallite.
The short-prismatic, face-rich, vaguely barrel-shaped siderite crystals, reaching 2 cm, are gemmy and yellow-brown, and rest on brassy yellow, discoidal crystals of pyrite pseudomorphous after (a first generation of) siderite, with lustrous black crystals of
stannite to 3 mm around the points of attachment--making for impressive toenail and small miniature-size specimens.
21 The mineral
stannite contains copper, iron and which other metal of which it is an ore?
Appearance of a grey film indicates dissolution as
stannite and must be avoided.
The place in question is an entirely landlocked, mountainous, somewhat mysterious-seeming country which boasts a long mining history and has a secure reputation for turning out world-class specimens of--oh, let's see--metallic species (andorite, pyrarygrite,
stannite, franckeite, cylindrite), other primary ores (cassiterite, ferberite), and glamorous phosphates (phosphophyl-lite, paravauxite, vivianite, ludlamite) such as we have long admired and lusted after.
Among the three different CZTS structures (kesterite structure (KS),
stannite structure (SS), and primitive mixed Cu-Au structure (PCMA)), the most reported one is kesterite structure (KS).
As in all books, there are some errors; for instance, the
stannite pictured in the book is really a sphalerite.
The XRD patterns for
stannite and kesterite CZTS, [Cu.sub.2]Sn[S.sub.3], and ZnS were very similar, and it was difficult to distinguish.