Sazhinite-(La)

Chemical formula: Na₃LaSi₆O₁₅·2H₂O

Sazhinite-(La) is a rare sodium and lanthanum silicate, forming small, creamy-white crystals with a platy habit.

## Characteristics Sazhinite-(La) is a hydrated sodium and lanthanum silicate belonging to the dalyite group. It occurs as small, platy or bladed crystals, which can form rosette-like or spherical aggregates. Typical specimens are creamy-white or colorless and exhibit a vitreous luster. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3. It is transparent to translucent. Its crystals show distinct cleavage in two directions. ## Colors and Varieties Sazhinite-(La) is typically creamy-white. In polarized light, it becomes colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral's name derives from its relation to sazhinite-(Ce), in which lanthanum (La) is the dominant rare earth element instead of cerium (Ce). It was first described in 1982 by Oleg von Knorring and Th. G. Sahama based on material from the Aris quarries in Namibia, which is its type locality.

Properties

Mohs hardness
3
Luster
Vitreous
Streak
White
Density
0
Cleavage
Parallel to {010} and {001}
Transparency
Transparent,Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Sazhinite-(La) can be identified by its platy crystal habit, often forming rosette-like aggregates. Its low hardness, creamy-white color, and occurrence in a specific geological environment – alkaline pegmatites and phonolites – are also characteristic. ## Distinguishing from Similar Minerals It can be confused with other minerals from the sazhinite group, such as sazhinite-(Ce). Differentiation requires advanced chemical analyses (e.g., EDS) to determine the dominant rare earth element. From other co-occurring white minerals (e.g., analcime, natrolite), it is distinguished by its crystal habit and excellent cleavage. ## Crystal Forms Crystals are platy or bladed, elongated along the crystallographic axis. They often form fan-shaped, rosette-like, or spherulitic aggregates, reaching several millimeters in diameter.

Geological environment

## Genesis Sazhinite-(La) is a magmatic mineral, crystallizing in the late stages within alkaline rock complexes. It is most commonly found in miarolitic cavities within phonolites and in nepheline syenite pegmatites. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals. At its type locality (Aris, Namibia), it has been found in association with eudialyte, lorenzenite, aegirine, microcline, nepheline, analcime, natrolite, tuperssuatsiaite, and villiaumite. ## Localities The most important and best-known occurrence of sazhinite-(La) is the phonolite quarries in Aris, Khomas Region, Namibia. This is its type locality, from which the best specimens originate. Beyond Namibia, its presence has also been reported in the Dara-i-Pioz alkaline complex in Tajikistan.

Rarity

Very rare

For collectors

## Quality Criteria Most valued by collectors are specimens with well-formed, sharp crystals forming aesthetic, rosette-like or fan-shaped aggregates. Contrast with the rock matrix and absence of damage are important. The size of aggregates also affects value, although even micromount specimens are sought after due to the mineral's rarity. ## Popular Localities Undoubtedly, the most desirable and well-known sazhinite-(La) specimens come from its type locality – the Aris quarries in Namibia. Specimens from this location set the standard for this mineral.

Care and storage

## Cleaning Due to its low hardness and potential reactivity, careful cleaning is recommended. It is safest to use compressed air to remove dust. If wet cleaning is necessary, use only distilled water and a soft brush, then quickly and thoroughly dry the specimen. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. Do not clean it with ultrasonics. Due to the presence of water in its structure, avoid high temperatures, which could cause dehydration. ## Storage Sazhinite-(La) specimens are best stored in separate, padded collector boxes to prevent abrasion and mechanical damage. They should be protected from dust and moisture.

External references

Sources

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