Britannica Sources used in this answer

Why can erythrite and annabergite help prospectors locate cobalt and nickel ores?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A labeled diagram of the periodic table entry for arsenic, showing its atomic number 33, symbol As, atomic weight 74.921595, electron configuration, and classification as an other nonmetal. Additional icons indicate arsenic is solid at room temperature, has a rhombohedral crystal structure, and weakly acidic oxides. — arsenic Properties of arsenic.

Erythrite and annabergite serve as valuable guides for prospectors because they act as visible indicators of cobalt and nickel deposits in the oxidized zones of ore bodies.1

These minerals are closely related, forming a complete solid-solution series where nickel can replace cobalt within the crystal structure. Their distinct colors allow prospectors to identify the presence of these metals through direct observation:1

Erythrite: Known for its characteristic crimson or peach-red color, it is a hydrated cobalt arsenate that signals the presence of cobalt-nickel-silver ores.1
Annabergite: As the nickel content in the mineral structure increases, the color shifts toward white, gray, or pale green. This hydrated nickel arsenate mineral is very similar to erythrite and serves as a visual marker for nickel-bearing deposits.123

By identifying these surface-level color variations in weathered outcrops, prospectors can locate the underlying mineralized veins.14