The Oxidized Zone

摘要

Some metal-bearing deposits (mainly copper, lead and zinc) in Arizona and elsewhere may have rich veins emplaced within limestone bodies. When surface weathering affects the ore, new minerals can form, particularly above the water table. This sequence of changes and the associated minerals are part of the oxidized zone. Characteristic of this zone, one may find a structure called a gossan, or iron hat. This mass of relatively worthless ore covers the much more valuable ore body and has a somewhat hollow structure where the original ore has been dissolved away. Further down, these same materials recombine to form different minerals that are of great interest to mineral collectors and museums. Similar deposits are known worldwide with similar mineralogy and origins.