Hanjiangite

Chemical formula: Ba₂Ca(V³⁺Al)(AlSi₃O₁₀)(OH)₂F(CO₃)₂

Hanjiangite is a rare mica group mineral, characterized by its yellowish-green color and occurrence as small, tabular crystals.

## Characteristics Hanjiangite is a complex silicate belonging to the mica group, specifically to the phengite group. It occurs as small, hexagonal or pseudohexagonal crystals with a tabular habit, often forming rosette-like or lamellar aggregates. Its characteristic feature is an intense, yellowish-green to dark-green color. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 4. It is transparent to translucent, and its density is approximately 3.69 g/cm³. It exhibits perfect cleavage in one plane, typical of mica group minerals, which causes it to easily split into thin, flexible lamellae. The fracture is splintery. ## Colors and Varieties The observed colors of hanjiangite range from yellowish-green to dark-green. No named varieties have been distinguished. ## History and Name The mineral's name comes from the Han River (Hanjiang), near which its type locality is situated. It was first described and approved as a new mineral species in 2012. ## Uses Due to its extreme rarity and small crystal size, hanjiangite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Greenish white
Density
3.69
Cleavage
on {001}
Fracture
Splintery
Transparency
Transparent,Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Key diagnostic features of hanjiangite include its characteristic yellowish-green color, perfect micaceous cleavage (splitting into thin lamellae), relatively low hardness, and a specific greenish-white streak. Its occurrence as small, hexagonal tabular crystals is also very typical. ## Distinguishing from Similar Minerals Hanjiangite can be confused with other green micas, such as muscovite (fuchsite variety), celadonite, or glauconite. It is distinguished from them by its higher density and unique chemical composition, containing barium and vanadium, which requires advanced analyses (e.g., EDS). ## Crystal Forms Hanjiangite forms small, thin, tabular crystals with a hexagonal outline. These crystals often occur in lamellar or rosette-like aggregates.

Geological environment

## Genesis Hanjiangite forms under low-temperature hydrothermal conditions. At its type locality, it was found in calcite veins cutting carbonate-siliceous rocks. ## Mineral Associations This mineral is associated with minerals such as calcite, celsian, quartz, pyrite, fluorite, and minerals from the chlorite group. ## Localities The only confirmed and described occurrence of hanjiangite in the world is its type locality - the Shiti mine in Hanbin District, Ankang Prefecture, Shaanxi Province, China.

Rarity

Very rare

For collectors

## Quality Criteria The most desirable hanjiangite specimens are those with well-formed, sharply terminated crystals of intense, vivid green color. An aesthetic composition on the rock matrix is also important, especially in association with contrasting minerals, such as white calcite. Due to the small size of the crystals, specimens visible to the naked eye (so-called macro-specimens) are particularly valued. ## Popular Localities All known collector specimens come from a single location in the world: the Shiti mine in China. This locality is the source of the best and only available specimens of this mineral on the market.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its perfect cleavage, avoid washing under running water and using ultrasonic cleaners, which could separate the mineral's lamellae. ## What to Avoid Avoid contact with chemicals, especially acids. The mineral is soft and susceptible to scratching, so it must be protected from contact with harder minerals. It should not be heated or exposed to prolonged strong sunlight. ## Storage It is recommended to store specimens in separate, padded display boxes to prevent mechanical damage and scratches. It is best to keep them in stable room conditions, away from moisture and dust.

External references

Sources

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