Hydrohonessite

Chemical formula: (Ni²⁺₁-xFe³⁺x)(S⁶⁺O₄)x/₂(OH)₂·nH₂O (x ₃x/₂)

Hydrohonessite is a rare, hydrated nickel and iron sulfate with a characteristic bright yellow color, occurring as thin coatings and crusts.

## Characteristics Hydrohonessite is a secondary mineral from the glaucocerinite group, chemically classified as a hydrated nickel and iron sulfate. It forms characteristic, bright yellow to greenish-yellow, thin coatings, crusts, and rosette-like or spherical aggregates. Due to its nature, it rarely occurs in well-formed crystals, and is most commonly found as microcrystalline aggregates covering other minerals. ## Physical Properties Due to its occurrence as thin and brittle coatings, precise determination of hardness is difficult. The luster of the mineral is described as waxy or dull. It is transparent to translucent. Density has not been accurately measured. ## Colors and Varieties This mineral is characterized by a uniform, bright yellow color, which can sometimes transition to greenish-yellow hues. No distinct color varieties or commercial varieties are recognized. ## History and Name The name hydrohonessite refers to its chemical composition (hydroxyl groups - "hydro") and its structural and chemical similarity to the mineral honessite. It was recognized as a distinct mineral in 1971. ## Uses Due to its rarity and form of occurrence, hydrohonessite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals or nickel minerals.

Properties

Luster: Waxy, Dull
Streak: Light yellow
Density: 0
Transparency: Transparent, Translucent
Crystal system: Hexagonal

Diagnostic features

## Identification Characteristic features of hydrohonessite include its bright yellow color and its occurrence as thin, brittle coatings and crusts on other minerals, especially in the oxidation zones of nickel deposits. It often forms small, rosette-like aggregates. ## Distinguishing from Similar Minerals Hydrohonessite can be confused with other yellow secondary sulfate minerals. From honessite, to which it is closely related, it is distinguished by its lighter color and lower iron content. Final differentiation from similar secondary minerals requires advanced chemical analyses (EDS) or X-ray diffraction (XRD). ## Crystal Forms Well-formed crystals are extremely rare. It typically forms microcrystalline, earthy, or waxy coatings, as well as small, spherical or rosette-like aggregates composed of tiny, tabular crystals.

Geological environment

## Genesis Hydrohonessite is a secondary mineral, forming in the oxidation (weathering) zones of nickel sulfide deposits. It forms as a result of the slow oxidation of primary nickel-bearing minerals, such as pentlandite or millerite, in the presence of water and oxygen. ## Mineral Associations It most commonly co-occurs with other secondary minerals of the oxidation zone, such as gypsum, morenosite, reevesite, as well as with relics of primary nickel and iron sulfides (pentlandite, pyrite, pyrrhotite, millerite) and with serpentine and magnetite. ## Localities The most important and classic locality (type locality), from which the best-known specimens originate, is the Otter Shoot nickel mine in the Kambalda region of Western Australia. This mineral has also been identified in other oxidation zones of nickel deposits worldwide, including Zimbabwe and Italy, but remains a very rare mineral.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, the most valuable specimens are those where hydrohonessite forms rich, clearly visible coatings of intense, bright yellow color. Samples where the mineral occurs in the form of distinct, rosette-like aggregates are also highly prized. Contrast with dark matrix rock and the presence of associated minerals enhance the visual appeal of the specimen. ## Popular Localities By far the most valued and sought-after specimens by collectors come from the type locality - the Otter Shoot mine in Kambalda, Western Australia. Specimens from other locations are extremely rare on the collector's market.

Care and storage

## Cleaning Hydrohonessite specimens are extremely delicate and brittle. They should be cleaned only very carefully, using a soft brush to remove dust. Any contact with water or other liquids is inadvisable, as it can damage or dissolve the delicate coatings. ## What to Avoid Contact with water, chemicals (including acids and detergents), and ultrasound should be strictly avoided. The mineral is sensitive to changes in humidity and temperature. It should not be exposed to direct sunlight, which can cause fading. ## Storage Specimens should be stored in stable conditions, preferably in closed, padded boxes or display cases, to protect them from mechanical damage, dust, and humidity changes. It should not be stored with harder minerals that could scratch or abrade it.

External references

https://www.mindat.org/min-1978.html