Vanderheydenite

Chemical formula: Zn₂+₆(PO₄)₂(S₆+O₄)(OH)₄·₇H₂O

A rare, secondary zinc phosphate of blue-green color, forming spherical aggregates and rosettes.

## Characteristics Vanderheydenite is a secondary hydrated zinc phosphate and sulfate, occurring in the oxidation zones of ore deposits. It forms characteristic spherical aggregates or rosettes composed of tiny, bladed crystals. Individual crystals are very small, rarely exceeding 0.2 mm in length, which makes the entire specimen appear as a delicate, fibrous coating. ## Physical Properties Vanderheydenite crystals are flexible and exhibit a vitreous luster. The mineral is translucent. Due to the small size of the crystals and their aggregated nature, determining hardness and density is difficult, but they are estimated to be approximately 2 and 2.85 g/cm³, respectively. ## Colors and Varieties This mineral occurs in a uniform, pale blue-green color. No varieties have been distinguished. ## History and Name The name vanderheydenite was given in honor of Eric Vanderheyden (born 1956), a Belgian mineral collector who first discovered this mineral. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2016 (IMA2016-025). The type locality is the "Block 14" mine in Broken Hill, New South Wales, Australia. ## Uses Due to its rarity and small size, vanderheydenite has no industrial applications. It is solely a mineral of scientific and collector interest, sought after by specialists in rare secondary minerals.

Properties

Mohs hardness: ~2
Luster: Vitreous
Streak: Pale blue-green
Density: 2.85
Cleavage: Perfect on {010}
Fracture: Splintery
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of vanderheydenite is based on its characteristic mode of occurrence – spherical or radial aggregates of a pale blue-green color. The locality (oxidation zone of zinc deposits) and associated minerals, such as hopeite, tarbuttite, or scholzite, are also crucial. Final confirmation requires advanced analytical methods (XRD, EDS). ## Distinguishing from similar minerals It can be confused with other secondary, blue-green zinc minerals, such as aurichalcite or rosasite, which, however, usually form acicular or fibrous crusts rather than spherical aggregates of bladed crystals. It is distinguished from scholzite by its color (scholzite is usually colorless or white). ## Crystal forms It forms very small, bladed crystals up to 0.2 mm long, gathered into spherical or hemispherical aggregates and rosettes reaching up to 0.5 mm in diameter.

Geological environment

## Genesis Vanderheydenite is a secondary mineral, forming in the oxidation zones of polymetallic deposits rich in zinc. It crystallizes in vugs and fissures in the presence of phosphate and sulfate-rich solutions, under conditions of low temperature and pressure. ## Mineral associations This mineral occurs in association with other secondary zinc minerals. At the type locality in Broken Hill, it was found in association with hopeite, tarbuttite, scholzite, as well as goethite and quartz. ## Localities The only confirmed and described occurrence of vanderheydenite in the world is its type locality: the "Block 14" mine in Broken Hill, Yancowinna County, New South Wales, Australia.

Rarity

Extremely rare

For collectors

## Quality criteria For collectors, the size and formation of the aggregates are most important. The most desirable specimens are those with numerous, well-defined spherical aggregates that clearly stand out from the matrix. The intensity of the blue-green color and the absence of damage to the delicate crystals also significantly increase the value of the specimen. ## Popular localities The only source of vanderheydenite specimens is the "Block 14" mine in Broken Hill, Australia, which automatically makes every specimen from this locality valuable from the perspective of mineral systematics and geography.

Care and storage

## Cleaning Due to the extreme delicacy and small size of the crystals, mechanical cleaning is not recommended. Specimens should be protected from dust, possibly by blowing compressed air from a safe distance. Any contact with water or a brush can destroy the aggregates. ## What to avoid Avoid contact with water, chemicals, acids, and detergents. The mineral is likely sensitive to changes in temperature and humidity, which can lead to its dehydration and disintegration. Avoid ultrasound and vibrations. ## Storage Vanderheydenite specimens should be stored exclusively in closed, stable containers (e.g., "perky box" type) to protect them from mechanical damage, dust, and humidity changes. It is not suitable for open display.

Sources

IMA Mineral List (CNMNC)