Calamine

Calamine is a historical term used to indicate a mixture of zinc-bearing minerals, primarily hemimorphite and smithsonite. This name, now considered obsolete in scientific mineralogy, was employed when the different zinc-rich mineral species were not clearly distinguished from one another.

Characteristics

Being a mixture, calamine exhibits variable characteristics depending on the predominant minerals. Hemimorphite imparts colorations ranging from white to bluish-green, while smithsonite may be gray, green, or yellowish. The general appearance is that of compact or botryoidal masses, often with a lustrous or earthy surface.

Genesis

It forms typically in the oxidation zone of zinc deposits, where primary minerals such as sphalerite undergo alteration through the action of meteoric waters. These processes lead to the formation of zinc carbonates and silicates that constitute calamine.

Varieties and Curiosities

Historically, calamine was the principal source of zinc for the production of brass. The term derives from the Latin «cadmia», used since antiquity to denote zinc minerals. Today, hemimorphite and smithsonite are preferred to be identified separately.

Importance for Collectors

Collectors value historical specimens labeled as calamine for their scientific-historical significance. However, the modern tendency is to reclassify these samples by correctly identifying the component minerals.

Italian Localities

In Sardinia, in the Iglesiente region, ancient deposits exist where calamine was once extracted. Some Alpine localities also present similar mineralizations, a legacy of past zinc-mining activity.