Tin does not occur naturally by itself, and must be extracted from a base compound, usually cassiterite, stannite, cylindrite, franckeite, canfieldite
, and teallite.
The specimen photos, by about 25 people, are predictably excellent; many, of course, have been published before, but who can complain about seeing, all over again, such magnificent things as the 3.6-cm Oruro andorite/stannite on page 26; the 9.2-cm Tasna bismuthinite on page 45; the 3.1-cm spherical Llallagua vauxite on page 50; the thumbnail-size Colquechaca canfieldite
on page 67; the surprising 8.2-cm Corocoro copper on page 79; the stunning cassiterites, ferberites, wavellites and apatites on several pages; and of course the great phosphophyl-lites, including Andy Seibel's breathtaking 5.2-cm matrix specimen on the front cover?
He also spent time in the mines in Bolivia and discovered the mineral that was eventually named after him: canfieldite
. His collection consisted of perhaps 9,000 specimens that were also given to the Smithsonian Institution.
From 1885 to 1887 he worked at the Cerro de Potosi mines in Bolivia, where he also collected minerals and discovered a new species later named canfieldite
in his honor.
The exhibit also held rare franckeite, andorite, helvite and canfieldite
specimens, all from South America.
The same fine Smithsonian case contained a 5 x 5-cm Bolivian phosphophyllite twin and a canfieldite
cluster from Bolivia with sharp gray 1-cm crystals; in a separate case (under constant armed guard) the Smithsonian folks placed the nearly-baseball-size 858-carat "Gachala" emerald crystal from Colombia, and a lavish emerald/diamond necklace once owned by Marjorie Merriweather Post.
As part of the middle stage mineralization in the northern periphery of the ore deposit, canfieldite
, hocartite, stannite, hessite, argentite, pyrargyrite, stephanite, polybasite and native silver were deposited, characteristically accompanied by minor cassiterite, arsenopyrite and chlorite.