Hemimorphite

Hemimorphite is a zinc silicate mineral with the chemical formula Zn4Si2O7(OH)2·H2O. It is a hydrous zinc silicate that commonly forms in the oxidized zones of zinc-bearing hydrothermal deposits, often as crusts, botryoidal masses, or occasionally prismatic crystals. Hemimorphite frequently occurs with other zinc minerals such as willemite and smithsonite and can form through alteration of zinc ore minerals under relatively low-temperature conditions.

The mineral is typically colorless, white, or pale blue to green, though darker or brownish hues can occur. It has a vitreous to waxy luster and is transparent to translucent. Crystals are usually elongated prisms, but the mineral more often appears as aggregated crusts or nodules. Hemimorphite displays a Mohs hardness of about 4.5 to 5 and a specific gravity near 3.4.

The name derives from Greek words meaning “half” and “shape,” referring to observations of partially developed crystal faces on some specimens. In hand specimens and collections, hemimorphite is valued as a mineral specimen for its color and luster and can occasionally be cut for ornamental use, though gem-quality material is rare.

Occurrence is worldwide, with production reported from many zinc-rich deposits in different regions. In addition to its practical association with zinc ores, hemimorphite is of interest to collectors and researchers studying hydrothermal ore-forming processes.