Although hemimorphite and smithsonite are different minerals with different chemical compositions and crystal structures, they have frequently been confused – especially when only simple tools were available and the specimens could not be subjected to destructive testing. Often a single specimen will be an intergrown mixture of hemimorphite and smithsonite. Until the mid-to-late 1800s, the name “calamine” was used for both minerals.

A few properties can help prevent confusion. Hemimorphite has a lower specific gravity (3.4 to 3.5) than smithsonite (4.3 to 4.5). Hemimorphite will not react with hydrochloric acid, but smithsonite will effervesce in contact with cold hydrochloric acid – but remember that the two minerals are often intergrown in a single specimen. Hemimorphite has perfect cleavage in one direction, but smithsonite has perfect cleavage in two directions which meet to form rhombic shapes.