Sahamalite-(Ce)

Chemical formula: Ce³⁺₂Mg(CO₃)₄

Sahamalite-(Ce) is a very rare carbonate group mineral, forming small, colorless to pale yellow crystals with a vitreous luster.

## Characteristics Sahamalite-(Ce) is a very rare mineral belonging to the carbonate group, with a complex chemical composition including cerium and magnesium. It occurs as very small, tabular or bladed crystals, rarely exceeding 1 mm in length. It typically forms radial aggregates or rosettes. It is colorless, white, or pale yellow, which, combined with the small size of the crystals, makes it difficult to observe with the naked eye. ## Physical Properties This mineral has a hardness of approximately 4 on the Mohs scale. It exhibits a vitreous luster and is transparent to translucent. The calculated density is about 3.95 g/cm³. It shows perfect cleavage in one direction. ## Colors and Varieties Sahamalite-(Ce) is usually colorless, white, or has a pale yellow hue. No color varieties or commercial varieties have been identified. ## History and Name The mineral was discovered in samples from the Mountain Pass mine in San Bernardino County, California, USA. It was described in 1953 by Howard T. Evans, Jr. and J. G. Mrose. The name "sahamalite" comes from the surname of the Japanese mineralogist Dr. Teruo Sahama (1906-1991) of the University of Tokyo, in recognition of his contribution to mineralogy and geochemistry. The suffix "-(Ce)" refers to the dominant rare earth element in its composition, which is cerium. ## Uses Due to its extreme rarity and small crystal size, sahamalite-(Ce) has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
4
Color
Colourless
Luster
Vitreous
Streak
White
Density
4.30
Cleavage
{010} poor, <mi>{_201}</mi> trace only.
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of sahamalite-(Ce) under amateur conditions is practically impossible due to its rarity and small crystal size. It requires advanced analytical methods such as X-ray diffraction (XRD) and chemical composition analysis (EDS/WDS). It is distinguished by its crystal habit and co-occurrence with other rare carbonate minerals. ## Distinguishing from Similar Minerals It can be confused with other rare earth carbonates from the same locality, such as Bastnäsite-(Ce), Parisite-(Ce), or Cordylite-(Ce). Differentiation requires specialized laboratory equipment. Bastnäsite usually has more vivid, yellow or brown colors, and Cordylite forms hexagonal crystals. ## Crystal Forms It forms very small, thin, tabular or bladed crystals, often flattened. These crystals combine into radial or rosette aggregates, as well as granular masses.

Geological environment

## Genesis Sahamalite-(Ce) forms in the late stages of hydrothermal processes within a carbonatite deposit. It crystallizes in rock fractures and cavities, where it precipitates from solutions rich in rare earth elements, magnesium, and carbonates. ## Mineral Associations This mineral co-occurs with other, often rare, minerals. In its type locality (Mountain Pass), it was found in association with barite, calcite, Bastnäsite-(Ce), Cordylite-(Ce), and a previously unknown mineral later identified as Daqingshanite-(Ce). ## Localities The only confirmed and well-documented occurrence of sahamalite-(Ce) in the world is its type locality - the Mountain Pass mine in the Mountain Pass Mining District, San Bernardino County, California, USA. This is the world's largest rare earth element deposit in carbonatites.

Rarity

Very rare

For collectors

## Quality Criteria The quality of sahamalite-(Ce) specimens is primarily assessed based on the richness and size of crystal aggregates on the rock matrix. Specimens with clearly formed, radial rosettes several millimeters in diameter are most valued. Due to its pale color, contrast with a darker matrix is desirable. The clarity and transparency of individual crystals are less important due to their microscopic size. ## Popular Localities The only source of collector specimens is the Mountain Pass mine in California. Material from this historic locality is highly prized by collectors specializing in rare minerals (so-called "micromounts").

Care and storage

## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its reactivity with acids, contact with water, especially if not distilled, should be avoided. The safest method is dry cleaning. ## What to Avoid Sahamalite-(Ce), as a carbonate, is sensitive to acids, with which it reacts vigorously. Contact with chemicals, ultrasound, and sudden temperature changes should be avoided. It should be protected from moisture. ## Storage It is recommended to store specimens in stable conditions, in closed, padded "micromount" boxes, to protect them from mechanical damage, dust, and moisture. Exposure to direct sunlight should be avoided, although there is no evidence of fading.

External references

Sources

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