Loughlinite
Chemical formula: Na₂Mg₃Si₆O₁₆·8H₂O
Loughlinite is a rare, hydrated sodium magnesium silicate that swells and transforms into sepiolite when in contact with water.
Properties
- Mohs hardness
- 1
- Color
- White
- Luster
- Pearly
- Streak
- white
- Density
- 2.165
- Cleavage
- Perfect on {100}, {010} and {001}
- Fracture
- Fibrous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Loughlinite can be identified by its fibrous structure, silky or pearly luster, and extremely low hardness (1 on the Mohs scale). It is very light and flexible. A key diagnostic feature is its reaction with water – when placed on the surface, it floats, then swells and changes into sepiolite. However, this test is destructive to the sample. ## Distinguishing from similar minerals Loughlinite is most often confused with sepiolite, into which it transforms. Sepiolite, however, is stable in water. It may also resemble other fibrous minerals, such as tremolite or chrysotile (asbestos), but it is much softer and lighter than these. Unlike them, loughlinite floats on water. ## Crystal forms This mineral occurs exclusively in the form of fibrous aggregates and felted masses. Individual fibers are flexible. It does not form macroscopic, well-developed crystals.
Geological environment
## Genesis Loughlinite is a mineral of hydrothermal or evaporitic origin. It forms under specific conditions within lacustrine sediments rich in sodium and magnesium. It occurs in shales, marls, and dolomites of the Green River Formation in the USA, which formed in a saline, alkaline lake environment. ## Mineral associations This mineral co-occurs with other minerals formed under similar conditions. It is most often accompanied by sepiolite (into which it transforms), analcime, dolomite, calcite, pyrite, as well as rarer evaporite minerals such as trona, shortite, and northupite. ## Localities The most important and classic locality for loughlinite is the Green River Formation, specifically mines in Sweetwater County (Wyoming) and Duchesne County (Utah) in the United States. These are the only confirmed, significant occurrences of this mineral worldwide.
Rarity
Very rare
For collectors
## Quality criteria The most prized loughlinite specimens are those consisting of pure, white, silky fibers forming dense and coherent aggregates. The size of the specimen and the absence of impurities and admixtures of other minerals are important. Due to the mineral's instability, its state of preservation is a crucial factor – specimens that have not yet transformed into sepiolite are the most valuable. The presence on the original rock matrix also increases its collectible value. ## Popular localities The only source of valuable collector specimens are the trona mines in the Green River Basin in Wyoming, USA. Specimens from this locality are considered type material and the most representative for this mineral species.
Care and storage
## Cleaning Cleaning loughlinite is highly problematic and generally discouraged. This mineral reacts with water, swelling and transforming into sepiolite. Any contact with liquids, including distilled water or alcohol, is risky. If absolutely necessary, dust can be attempted to be removed using compressed air from a distance or a very soft, dry brush. ## What to avoid Contact with water and any moisture must be strictly avoided. Storage in a humid environment leads to its irreversible degradation. Ultrasonic cleaners, chemical agents, and sudden temperature changes should also be avoided. Due to its low hardness, it is extremely susceptible to mechanical damage. ## Storage Loughlinite specimens require special storage conditions. They should ideally be kept in tightly sealed containers (e.g., "perky boxes") with a desiccant, such as silica gel. It should be protected from dust, sunlight, and vibrations. Display should only take place in a controlled, dry environment.