Hemimorphite

Hemimorphite is a silicate mineral containing zinc, silicon, oxygen and water. Its name comes from its crystals ending in different faces at the two ends (hemimorphism). It forms near the surface of zinc deposits, about 54 % of its weight is zinc, and it is a minor ore of zinc. Its blue and blue-green translucent masses are cut as cabochons and beads.

Zinc ore: Up to 54 % of its weight is zinc. For centuries it was part of the “calamine” that was mined, together with smithsonite, from the upper parts of zinc and lead ores. Ornamental stone: Blue and blue-green translucent masses are cut as cabochons and beads; because it is soft, it needs care in jewellery. Collecting: Bright crystals whose two ends differ, and fan-shaped clusters, are sought by mineral collectors.

It has a hardness of 4.5–5 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 3.4–3.53 g/cm³.

Its best-known localities: Ojuela mine, Mapimí, Durango, Mexico; Kelmis (La Calamine, Moresnet), Belgium; Tarnowskie Góry, Silesia, Poland; Santa Eulalia, Chihuahua, Mexico; Padaeng, Mae Sot, Tak, Thailand.

Known localities in Türkiye: Aladağlar (Yahyalı area), Kayseri, Türkiye.

It does not fizz in acid; the very similar smithsonite does. Its hardness is 4.5–5. Its specific gravity is about 3.4–3.5, distinctly lighter than smithsonite (about 4.3–4.5). Its crystals are thin and plate-like and often form fans or cockscomb-like clusters; the two ends of a crystal terminate differently. As masses it is grape-like, stalactitic or crusty. Smithsonite: it looks very much like hemimorphite and occurs in the same deposits; for centuries both were called “calamine”. It is told apart by fizzing in acid and by being heavier.

On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. As an ornamental stone its value depends on the vividness of the colour (bright blue and blue-green tones), translucency and texture; colourless or pale stones are less sought after. In collecting, large, bright, well-formed crystals and specimens from famous places such as Ojuela or Santa Eulalia are valued. Being of medium hardness (4.5–5) and cleavable, it needs care in jewellery. As a zinc ore it is a minor ore; its value depends on its grade and on mining conditions.

Kunz reports that Mexican Indian workers in the mines of Sonora and western Chihuahua placed a piece of blue calamine (hemimorphite) beside the small cross and candle shrine they set up where they worked; he suggests it may be because of the stone's beautiful colour or because they take it for turquoise. Today crystal-therapy practitioners claim that hemimorphite is linked to the throat chakra and makes it easier to communicate and express feelings. The same circles say the stone helps to process sadness, increases confidence and joy, and makes it easier to connect with angels and spirit guides. There is no scientific evidence that hemimorphite affects communication, confidence or mood, or puts anyone in touch with spiritual beings. The practice Kunz describes is a religious act and does not show that the stone itself has a power. Hemimorphite contains zinc: the stone should not be put in water to make a drinkable “elixir”, and its dust should not be breathed in. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.