Cianciulliite

Chemical formula: Mg<sub>2</sub>Mn<sup>2+</sup>Zn<sup>2+</sup><sub>2</sub>(OH)<sub>10</sub>·2-4H<sub>2</sub>O

Cianciulliite is a very rare manganese, zinc, and magnesium hydroxysulfate, forming microscopic, orange crystals with a hexagonal outline.

## Characteristics Cianciulliite is a hydrated manganese, zinc, and magnesium hydroxysulfate, occurring as extremely small, tabular crystals. They typically form rosette-like or spherulitic aggregates, and individual crystals rarely exceed 0.5 mm. Due to their size, a microscope is essential for their observation. The crystals have a characteristic hexagonal outline and are thin, resembling flakes. ## Physical Properties Cianciulliite crystals are very soft, with a Mohs hardness of only 1. They are also very brittle and flexible. The luster is pearly on cleavage surfaces and vitreous on other faces. The mineral is transparent to translucent. ## Colors and Varieties Cianciulliite occurs in a uniform, orange color. No color or commercial varieties are distinguished. ## History and Name The mineral was named in honor of John Cianciulli (born 1953), an American mineral collector from New Jersey, who specialized in minerals from Franklin and Sterling Hill and was the first to notice this mineral. It was described and approved as a new mineral species in 1991 by Pete J. Dunn, Donald R. Peacor, Shu-Chun Su, Fred J. Wicks, and Richard A. Gault. ## Uses Cianciulliite has no industrial applications. Its significance is purely scientific and collectible, being an object of desire among collectors specializing in rare minerals and those from the Franklin mine.

Properties

Mohs hardness
1
Luster
Pearly
Streak
Light orange
Density
3.06
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Cianciulliite is identified by its unique appearance under a microscope: orange, hexagonal, tabular crystals forming rosette aggregates. The locality – the Franklin mine in New Jersey – is also key. Due to its size, positive identification requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals At first glance, it may be confused with other microminerals from Franklin, such as mcgovernite or holdenite, which can also form small, hexagonal crystals. However, cianciulliite is distinguished by its characteristic orange color and specific aggregate morphology. Final distinction requires chemical composition analysis. ## Crystal Forms The mineral forms thin, tabular crystals with a hexagonal outline. These crystals group into rosettes, spherulitic aggregates, or irregular clusters on the surface of the host rock (matrix).

Geological environment

## Genesis Cianciulliite is a secondary mineral, formed as a result of hydrothermal processes in zinc, manganese, and iron deposits. It occurs in fractures and small voids within calcite. Its formation is associated with the contact metamorphism of the Franklin ore deposit. ## Mineral Associations This mineral co-occurs with other, often rare, minerals from the Franklin deposit. It is most commonly found in association with calcite, franklinite, willemite, zincite, as well as kraisslite, mcgovernite, holdenite, and kutarovite. ## Localities The only confirmed occurrence of cianciulliite in the world (type locality) is the Franklin mine in Sussex County, New Jersey, USA. This is a classic locality for many rare minerals, including numerous zinc and manganese species.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a cianciulliite specimen is primarily assessed based on the richness and aesthetics of the microcrystals. Specimens with numerous, well-formed, orange rosettes, clearly contrasting with a light background, most often white calcite, are most highly valued. The size of individual crystals, although always microscopic, is also important – larger and sharper crystals increase the specimen's value. Color contrast with associated minerals is highly desirable. ## Popular Localities The only source of cianciulliite specimens is its type locality – the Franklin mine in New Jersey, USA. All specimens available on the collector's market come from this single location, making them particularly valuable for specialists and collectors of systematic minerals and those focused on this specific locality.

Care and storage

## Cleaning Cianciulliite specimens are extremely delicate and susceptible to mechanical damage. Cleaning should be kept to an absolute minimum. If necessary, a very gentle stream of compressed air can be used to remove loose dust particles. Any contact with water or other liquids should be avoided. ## What to Avoid Contact with water, chemicals, ultrasound, and any mechanical tools should be strictly avoided. The crystals are extremely soft (Mohs hardness 1) and brittle, so even the slightest touch can destroy them. The specimen should be protected from sudden changes in temperature and humidity. ## Storage Specimens should be stored only in stable, sealed "micromount" containers to protect them from dust, humidity, and physical damage. Storage in a dry place is crucial. Due to the microscopic size of the crystals, they are not suitable for display outside of specialized boxes.

Sources

Read more