Kapundaite

Chemical formula: CaNaFe³⁺₄(PO₄)₄(OH)₃·₅H₂O

Kapundaite is a rare, hydrated sodium, calcium, and iron phosphate, forming aggregates of tiny, golden-yellow crystals.

## Characteristics Kapundaite is a hydrated sodium, calcium, and iron phosphate. It occurs as aggregates of small, bladed or acicular crystals, rarely exceeding 1 mm in length. It forms radiating aggregates, rosettes, as well as spherulitic or fibrous crusts on the surface of host rocks. Its appearance is delicate, and the aggregates can be very photogenic despite their small size. ## Physical Properties This mineral is characterized by a relatively low hardness of 3 on the Mohs scale, making it susceptible to scratching. Its density is approximately 2.93 g/cm³. The crystals are transparent to translucent and exhibit a vitreous luster. Due to its small size and fragility, it is a very delicate mineral. ## Colors and Varieties Kapundaite occurs in uniform shades of yellow – from pale yellow to intense, golden-yellow. No color or commercial varieties are distinguished. ## History and Name The mineral's name comes from the historic mining town of Kapunda in South Australia, located near its discovery site. Kapundaite was first identified in material collected in 1980 at Tom's Quarry, but it was only described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2010. ## Uses Kapundaite has no industrial applications. It is solely a mineral of scientific and collecting interest, sought after by collectors specializing in rare phosphates or minerals from specific localities.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Yellow
Density: 2.93
Fracture: Irregular/Uneven
Transparency: Transparent,Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Kapundaite can be identified by its characteristic golden-yellow color, radiating or spherulitic aggregates of tiny, acicular crystals, and its occurrence in paragenesis with other secondary phosphates. A yellow streak is also a helpful feature. However, definitive identification requires advanced analytical methods such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other yellow secondary iron phosphates such as cacoxenite, strengite, or cyrilovite. It is distinguished from them by its specific aggregate form (thin, radiating needles) and, most importantly, its unique chemical composition containing both sodium and calcium. Many of these minerals also have different hardness or streak colors. ## Crystal Forms Kapundaite crystals are very small, typically bladed or acicular. They most often form radiating aggregates, where individual crystals spread out from a common center. They also occur as spherical aggregates (spherulites) and as thin, fibrous crusts.

Geological environment

## Genesis Kapundaite is a secondary phosphate mineral. It forms in the oxidation zones of phosphate deposits, resulting from the alteration of primary phosphorus and iron-bearing minerals under the influence of surface waters. Its crystallization occurs in fissures and voids of sedimentary rocks rich in phosphates. ## Mineral Associations This mineral co-occurs with other secondary phosphates. At the type locality (Tom's Quarry), it was found in association with, among others, cyrilovite, strengite, rockbridgeite, dufrenite, as well as goethite and quartz. ## Localities The most important and best-documented occurrence of kapundaite is its type locality: Tom's Quarry near Koonunga, South Australia. This is a historic phosphate mine known for the occurrence of many rare minerals from this group. Beyond this site, its occurrence has not been confirmed in other regions of the world.

Rarity

Very rare

For collectors

## Quality Criteria The most prized kapundaite specimens are those with well-formed, rich, spherulitic or radiating aggregates of intense, golden-yellow color. Contrast with a darker host rock is important, enhancing the mineral's aesthetic appeal. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. A large coverage area of the rock by the mineral also increases its value. ## Popular Localities The only source of collectible kapundaite specimens is its type locality: Tom's Quarry in South Australia. Specimens from this location are sought after by collectors specializing in mineral systematics, rare species, and minerals from type localities.

Care and storage

## Cleaning Kapundaite specimens should be cleaned with the utmost care, preferably using compressed air to remove dust. Any contact with water or a brush is risky due to the fragility and small size of the crystals. If liquid is necessary, it is recommended to very carefully wipe with a brush moistened with isopropyl alcohol, avoiding soaking the host rock. ## What to Avoid Avoid contact with water, acids, and other chemicals. The mineral is very soft and brittle, so it must be protected from impacts, vibrations, and scratching. It should not be cleaned with ultrasonics. Prolonged exposure to strong sunlight is not recommended. ## Storage Kapundaite specimens are best stored in sealed, padded "micromount" boxes, which protect them from dust, mechanical damage, and moisture. Display should be in stable conditions, away from sources of vibration and direct light.

External references

https://www.mindat.org/min-39673.html