Hawleyite

Chemical formula: Cd²⁺S²⁻

Hawleyite is a rare cadmium sulfide forming bright yellow, earthy coatings, being a dimorphic form of greenockite.

## Characteristics Hawleyite is a cadmium sulfide belonging to the sphalerite group. It most commonly occurs as bright yellow, powdery, or earthy coatings and crusts on other minerals, mainly on sphalerite. It rarely forms tiny, poorly developed crystals. It is soft and brittle. Due to its mode of occurrence, individual physical properties can be difficult to observe with the naked eye. ## Physical Properties The mineral is characterized by low hardness, ranging from 2.5-3 on the Mohs scale. Its luster is described as earthy or dull, which is typical for its powdery aggregates. It is translucent to opaque. ## Colors and Varieties Hawleyite occurs in a characteristic, bright yellow color. No color or commercial varieties are distinguished. ## History and Name The mineral's name honors James Edwin Hawley (1897-1965), a Canadian mineralogist and professor at Queen's University in Kingston, Ontario. The mineral was first described in 1955 by R.J. Traill and R.W. Boyle based on specimens from the Hector-Calumet mine in the Mayo District, Yukon, Canada. ## Uses Due to its rarity and mode of occurrence, hawleyite has no industrial applications. It is solely an object of interest for collectors specializing in rare or systematic minerals.

Properties

Mohs hardness: 2.5-3
Luster: Earthy
Streak: Light yellow
Density: 0
Transparency: Translucent, Opaque
Crystal system: Isometric

Diagnostic features

## Identification Hawleyite is most easily recognized by its characteristic mode of occurrence - as a bright yellow, powdery coating on sphalerite or other sulfides. Its color and earthy texture are key diagnostic features in the field and in collections. ## Distinguishing from Similar Minerals Hawleyite is nearly impossible to distinguish from greenockite (another, hexagonal polymorph of cadmium sulfide) without advanced analytical methods (e.g., X-ray diffraction). However, greenockite more commonly forms visible crystals. It can also be confused with other yellow secondary coatings, such as native sulfur, which, however, has a lower specific gravity and a characteristic odor when heated. ## Crystal Forms It crystallizes in the isometric system. However, crystals are extremely rare and microscopic in size. It usually forms powdery, earthy, or sooty aggregates and thin coatings.

Geological environment

## Origin Hawleyite is a secondary mineral. It forms in the oxidation (weathering) zones of ore deposits, mainly as a result of the weathering of cadmium-rich sphalerite. It forms under low-temperature conditions, often in voids and fractures of sedimentary rocks or hydrothermal veins. ## Mineral Associations It most commonly occurs associated with sphalerite (as a coating on its surface), as well as with greenockite, smithsonite, and other secondary zinc minerals. ## Localities The most important and type locality is the Hector-Calumet mine in the Mayo region of Yukon (Canada). It is also known from a few other localities worldwide with zinc and lead deposits, but it remains a rare mineral everywhere.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, the most important factors are the intensity and uniformity of the yellow coating's color and the richness of coverage on the matrix. Contrast with darker sphalerite or another substrate mineral enhances the visual appeal of the specimen. Due to the mineral's nature, clarity and crystal form are not typical criteria for evaluation. ## Notable Localities By far the most appreciated and sought-after specimens by collectors come from the type locality in Yukon, Canada. They are historically the most significant and serve as the benchmark for this mineral.

Care and storage

## Cleaning Specimens with hawleyite coatings are extremely delicate. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used from a safe distance to remove loose dust. Any contact with water and brushes should be avoided. ## What to Avoid Hawleyite is soft and brittle, so impacts and abrasion should be avoided. As a sulfide, it may be sensitive to chemicals, especially acids. Protect it from moisture and sudden temperature changes. ## Storage Specimens should be stored in closed, stable containers (e.g., membrane boxes or softly lined boxes) to protect delicate coatings from mechanical damage and dust. Store in a dry place.