Hodgesmithite

Chemical formula: (Cu₂+,Zn₂+)₆Zn₂+(S₆+O₄)₂(OH)₁₀·₃H₂O

Hodgesmithite is a very rare, secondary copper and zinc sulfate, forming blue-green, spherical aggregates and rosettes.

## Characteristics Hodgesmithite is a hydrated copper and zinc sulfate, occurring as microscopic, spherical aggregates or rosettes. Individual crystals are in the form of lamellae or tabular crystals, not exceeding 100 micrometers in size. Due to its size, it is a mineral primarily observed under magnification. It forms thin coatings and crusts on host rocks. ## Physical Properties Crystals are very small and brittle. The luster is described as vitreous to pearly on cleavage surfaces. The mineral is translucent. Due to the microscopic nature of the crystals, many physical properties, such as hardness or density, have not been precisely measured. ## Colors and Varieties Hodgesmithite has a characteristic, vivid blue-green color. No varieties have been distinguished. ## History and Name The mineral was discovered in the Tsumeb Mine in Namibia, famous for its exceptional and rare minerals. It was described in 2017 by Stuart J. Mills and co-workers. The name honors Dr. Joel Hodgesmith (born 1957), an American mineral collector and physician, who specialized in Tsumeb minerals and provided the sample for study. ## Applications Due to its extreme rarity and microscopic size, hodgesmithite has no industrial application. It is solely an object of scientific and collector interest for specialized micromount mineral collectors.

Properties

Mohs hardness: 2
Luster: Vitreous
Streak: Pale blue
Density: 3.33
Cleavage: Perfect on {010}
Fracture: Splintery
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of hodgesmithite under amateur conditions is practically impossible. It requires specialized analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). A preliminary indication may be its blue-green color, the form of spherical aggregates, and its occurrence in paragenesis with other secondary zinc and copper minerals in Tsumeb. ## Distinguishing from Similar Minerals It can be confused with many other secondary copper and zinc minerals of similar color, such as aurichalcite, rosasite, zincrosasite, or ktenasite. Aurichalcite often forms acicular or fibrous aggregates, while hodgesmithite forms spherical aggregates composed of lamellae. Definitive distinction is only possible using advanced laboratory techniques. ## Crystal Forms Hodgesmithite forms spherical aggregates and rosettes up to 0.1 mm in diameter, composed of very small, lamellar or tabular crystals.

Geological environment

## Genesis Hodgesmithite is a secondary mineral, forming in the oxidation zone (gossan) of polymetallic deposits rich in copper and zinc. It forms as a result of the weathering of primary sulfides, such as chalcopyrite and sphalerite, in the presence of carbonate host rocks (e.g., dolomites). ## Mineral Associations This mineral co-occurs with other secondary minerals of the oxidation zone. In its type locality (Tsumeb), it was found in association with ktenasite, linarite, gypsum, anglesite, cerussite, and quartz. ## Localities The only confirmed locality of hodgesmithite in the world is the Tsumeb Mine in the Oshikoto Region, Namibia. This is the so-called type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria For micromount collectors, the most valuable specimens are those with well-formed, distinct spherical aggregates of intense, blue-green color. Contrast with the rock matrix and the presence of rare associated minerals are also important. Due to its microscopic nature, the quality of the photomicrograph documenting the specimen is crucial. ## Popular Localities The only source of hodgesmithite specimens is the historic Tsumeb Mine in Namibia. All samples available on the collector's market originate from this single location.

Care and storage

## Cleaning Specimens of hodgesmithite should generally not be cleaned mechanically or chemically. Dust can be removed very carefully using a photographic air blower or compressed air from a distance. Any contact with water or chemicals can damage or destroy the delicate crystals. ## What to Avoid Contact with water, acids, detergents, and other cleaning agents must be absolutely avoided. The mineral is likely sensitive to high temperatures and prolonged exposure to strong light. It should be protected from moisture. ## Storage Hodgesmithite specimens should be stored under stable conditions, in closed, airtight containers (so-called micromount boxes) to protect them from dust, moisture, and mechanical damage. It is best to keep them in a dry place, away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)