Kingite

Chemical formula: Al<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>F<sub>2</sub>(OH)·7H<sub>2</sub>O

Kingite is a rare, hydrated aluminum phosphate, forming small, white aggregates and crusts in weathered phosphate rocks.

## Characteristics Kingite is a rare mineral from the phosphate group, occurring as very small, almost microscopic crystals. It typically forms compact, earthy or chalk-like aggregates, as well as thin crusts and coatings on other minerals. Individual crystals, visible only under high magnification, are in the form of small, flattened tablets. Due to the small size of the crystals, its macroscopic features are difficult to observe, and specimens most often appear as white, brittle masses. ## Physical Properties This mineral is very soft, with a Mohs hardness of about 2.5. It is light, with a density close to 2.2-2.3 g/cm³. It exhibits a white, earthy luster, and individual crystals may have a pearly luster. It is translucent to opaque. ## Colors and Varieties Kingite is usually white, snow-white, or colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral's name honors geologist Dr. D. King of the South Australian Department of Mines, who first found this mineral. It was described and approved as a new mineral species in 1957 by K. Norrish, L.K. Rogers, and J.S. Shiels based on samples from the Robertstown phosphate mine in South Australia. ## Uses Kingite has no industrial or commercial applications. Its significance is purely scientific and collectible, as a rare and interesting mineralogical species.

Properties

Mohs hardness
2.5
Luster
Pearly
Streak
White
Density
2.2-2.3
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Triclinic

Diagnostic features

## Identification Field identification of kingite is practically impossible without specialized equipment. In a collection, it is identified by its typical appearance – white, earthy, or chalk-like aggregates on the host rock. Knowledge of the specimen's origin location is crucial, as it occurs in very few places worldwide. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Kingite can be easily confused with other white, earthy secondary minerals such as wavellite, crandallite, wardite, or evansite. Distinguishing them based on visual characteristics is unreliable. Wavellite often forms characteristic radial aggregates, which can be a clue, but certainty is only provided by chemical or structural analysis. ## Crystal Forms Kingite crystallizes as very small, tabular crystals that are rarely visible to the naked eye. Most often, it forms compact, earthy masses, spherulitic aggregates, or thin crusts and coatings.

Geological environment

## Genesis Kingite is a secondary phosphate mineral that forms in the weathering zones of phosphorite or guano deposits. It forms as a result of the interaction of phosphorus-rich solutions with aluminous minerals or aluminosilicate rocks under low temperature and pressure conditions. ## Mineral Associations This mineral co-occurs with other secondary phosphate minerals. It is most often found in association with wavellite, crandallite, wardite, apatite, evansite, as well as clay minerals and iron oxides (goethite, limonite). ## Localities The most important and classic locality for kingite is the phosphate mine near Robertstown in South Australia, from which the type material originates. It has also been found at Tom’s Phosphate Quarry in Kapunda, Australia. Outside Australia, its occurrence has been reported in small quantities in Spain (in El Pindal Cave in Asturias) and at the Silver Coin mine in Valmy, Nevada, USA.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a kingite specimen is primarily assessed based on the richness and purity of the white aggregates on the host rock. As it is a microcrystalline mineral, specimens with well-formed, though still very small, spherulites or thick crusts are sought after. Contrast with a darker host rock enhances visual appeal. The size of individual crystals is not a criterion, as they are usually microscopic. ## Popular Localities By far the most valued and sought-after specimens by collectors come from the type locality – Robertstown in South Australia. Material from this locality is considered classic for this species.

Care and storage

## Cleaning Due to its extreme brittleness and softness, kingite should not be mechanically cleaned. Contact with water, which can damage or dissolve delicate aggregates, should be avoided. The safest method is gentle blowing with compressed air from a safe distance to remove dust. ## What to Avoid Contact with water, acids, and other chemicals must be absolutely avoided. The mineral is very soft and brittle, so it should be protected from any impacts, scratches, and vibrations. It should not be heated, as it is a hydrated mineral and will lose water, leading to its destruction. ## Storage Kingite specimens should be stored in stable, sealed "micromount" containers that protect them from mechanical damage, dust, and humidity changes. Avoid exposure to direct sunlight and store in a dry place.

Sources

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