Orthojoaquinite-(Ce)

Chemical formula: NaBa<sub>2</sub>Fe<sup>2+</sup>Ce<sup>3+</sup><sub>2</sub>Ti<sup>4+</sup><sub>2</sub>(SiO<sub>3</sub>)<sub>8</sub>O<sub>2</sub>(O,OH)·H<sub>2</sub>O

The orthorhombic analogue of joaquinite-(Ce), a rare mineral from the joaquinite group, distinguished by its orthorhombic crystal system.

## Characteristics Orthojaquinite-(Ce) is a rare mineral belonging to the joaquinite group. It forms small, tabular or prismatic crystals, often with a square or octagonal outline, reaching up to 1 mm in size. It typically occurs as single, disseminated crystals within the host rock. It is the orthorhombic analogue of monoclinic joaquinite-(Ce). ## Physical Properties The mineral is characterized by a hardness of 5.5 on the Mohs scale and a density of approximately 4.09 g/cm³. It has a vitreous luster and is transparent to translucent. It does not exhibit fluorescence under ultraviolet light. ## Colors and Varieties Orthojaquinite-(Ce) most commonly exhibits colors ranging from yellow to yellowish-brown or honey-yellow. No specific varieties have been distinguished. ## History and Name The mineral's name refers to its orthorhombic crystal system and its association with another mineral from this group, joaquinite. The "-(Ce)" suffix indicates cerium as the dominant rare-earth element in its chemical composition. It was first described in 1982 by S. E. Haggerty and co-workers based on material from the Jagersfontein diamond mine in the Republic of South Africa. ## Applications Due to its rarity and small crystal size, orthojaquinite-(Ce) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
5.5
Luster
Vitreous
Streak
Pale yellow
Density
4.09
Cleavage
Good on {100} and {010}
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Orthojaquinite-(Ce) is difficult to identify visually without specialized equipment. Its characteristic features include small, yellowish-brown, tabular crystals with a vitreous luster, embedded in a specific host rock (e.g., benitoite-bearing rock). Positive identification requires advanced methods such as chemical analysis (EDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other minerals from the joaquinite group, such as joaquinite-(Ce) or strontiojoaquinite. Differentiation is almost exclusively possible based on chemical composition and crystal structure analysis. Visually, it is practically indistinguishable from joaquinite-(Ce). ## Crystal Forms Crystals are typically small, with a tabular or short-prismatic habit. They occur as single, well-formed crystals embedded in other minerals.

Geological environment

## Genesis Orthojaquinite-(Ce) is a hydrothermal mineral. It forms in the late stages of crystallization in carbonatite veins or in altered fragments of serpentinites rich in sodium, titanium, and rare-earth elements. In its type locality (Jagersfontein), it occurs in gabbro xenoliths within kimberlite. ## Mineral Associations This mineral co-occurs with minerals such as benitoite, neptunite, natrolite, joaquinite-(Ce), albite, aegirine, jonesite, and titanite. ## Localities The most important and confirmed occurrences of orthojaquinite-(Ce) are: - Jagersfontein diamond mine, Free State, Republic of South Africa (type locality). - San Benito County, California, USA, especially in the Dallas Gem and Junnila mines.

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals of intense, honey-yellow color. The presence of the mineral on an aesthetic rock matrix is crucial, especially when accompanied by other rare minerals such as benitoite or neptunite. Due to the small size of the crystals, their size also significantly affects the value of the specimen. ## Popular Localities By far the most sought-after specimens come from San Benito County, California, which is the source of the world's best joaquinite group mineral specimens.

Care and storage

## Cleaning It is recommended to clean only with a soft brush to remove dust. The use of water, especially with detergents, is not advisable due to the risk of damaging delicate crystals and the host rock. ## What to Avoid Avoid contact with all chemicals, including acids and strong bases. The mineral is sensitive to rapid temperature changes. It should not be cleaned in ultrasonic or steam cleaners. ## Storage Specimens should be stored in stable conditions, away from direct sunlight, dust, and moisture. It is best to place them in a closed display box or cabinet to minimize the risk of mechanical damage.

Sources

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