Gysinite-(Ce)

Chemical formula: Pb<sup>2+</sup>Ce<sup>3+</sup>(CO<sub>3</sub>)<sub>2</sub>(OH)(H<sub>2</sub>O)

A rare lead and cerium mineral, forming small, prismatic crystals of a pinkish-violet color and vitreous luster.

## Characteristics Gysinite-(Ce) is a hydrated lead and cerium hydroxycarbonate, belonging to the ancylite group. It occurs as very small, prismatic or tabular crystals, rarely exceeding 1 mm in length. It also forms rosette aggregates and radial clusters. It is a transparent to translucent mineral with a vitreous luster. ## Physical Properties The mineral is characterized by a Mohs hardness of approximately 4-4.5. Its density is quite high, around 4.83 g/cm³. It does not exhibit cleavage, and its fracture is uneven. It is neither radioactive nor fluorescent. ## Colors and Varieties The typical color of gysinite-(Ce) is pinkish-violet to pale pink. Some specimens may be colorless. No commercial or color varieties are distinguished. ## History and Name The mineral is named in honor of Professor Michel Gysin (1895-1977), director of the Institute of Mineralogy at the University of Geneva, Switzerland, in recognition of his contributions to mineralogy. The "-(Ce)" suffix indicates the dominant rare earth element in its composition – cerium. The mineral was approved by the IMA in 1982, and its discovery was made on material from the Shinkolobwe mine in the Democratic Republic of Congo.

Properties

Mohs hardness
4-4.5
Luster
Vitreous
Streak
White
Density
4.83
Cleavage
None
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Amateur identification of gysinite-(Ce) is practically impossible due to its rarity and small crystal size. The characteristic pinkish-violet color, high density, and co-occurrence with other secondary minerals in the oxidation zones of sulfide deposits can be indicative. Definitive identification requires advanced analytical methods, such as EDS spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other minerals from the ancylite group, such as ancylite-(Ce) or calkinsite-(Ce), from which it can only be distinguished by chemical analysis. Visually, it may resemble some zeolites or other secondary carbonates, but its high density (due to lead content) is a distinguishing feature. ## Crystal Forms It forms elongated, prismatic crystals with a rhombic cross-section, often terminated with a double pyramid. It also occurs as rosette and radial aggregates, growing on other minerals.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation zones (gossans) of hydrothermal ore deposits rich in lead and rare earth elements. It forms as a result of the weathering of primary minerals containing these elements, in a carbonate-rich environment. ## Mineral Associations It most commonly co-occurs with malachite, cerussite, quartz, wulfenite, kasolite, schopenite-(Ce), and bijvoetite-(Y). In its type locality (Shinkolobwe), it was found in association with uraninite and secondary uranium minerals. ## Localities The most important and confirmed localities for gysinite-(Ce) are: - Shinkolobwe Mine, Democratic Republic of Congo (type locality). - Kasompi Mine, Democratic Republic of Congo. - Bwana Mkubwa Mine, Zambia. - Clara Mine in the Black Forest, Germany. - Nakauri Mine, Aichi Prefecture, Japan.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a gysinite-(Ce) specimen primarily depends on the crystal habit and size. Well-formed, sharply terminated, transparent crystals with an intense, pinkish-violet color are most valued. Their arrangement on the rock matrix and aesthetic associations with other minerals, e.g., contrasting green malachite, are also important. ## Popular Localities The best specimens, serving as a benchmark for this mineral, come from mines in the Democratic Republic of Congo, especially from Kasompi. Specimens from the Clara Mine in Germany are also prized by collectors specializing in systematic minerals and micromounts.

Care and storage

## Cleaning Due to the small size of the crystals and their fragility, mechanical cleaning is not recommended. If necessary, compressed air can be used to remove dust. Contact with water, especially deionized water, should be kept to a minimum. ## What to Avoid Avoid contact with acids, which can react violently with the mineral (effervesces in hydrochloric acid). Protect it from ultrasound, high temperatures, and sudden thermal changes. Store away from chemicals. ## Storage Gysinite-(Ce) specimens are usually very small and fragile, so it is best to store them in sealed "micromount" boxes, protecting them from dust and mechanical damage. Avoid exposure to direct sunlight, although there is no evidence of fading.

Sources

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