Leifite
Chemical formula: Na<sub>7</sub>Be<sub>2</sub>(Si<sub>15</sub>Al<sub>3</sub>)O<sub>39</sub>(F,OH)<sub>2</sub>
Leifite is a rare beryllium and sodium silicate, forming characteristic radial aggregates of acicular, white crystals.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous, Silky
- Streak
- White
- Density
- 2.5 - 2.6
- Cleavage
- Good on {10-10}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification The key diagnostic feature of leifite is its mode of occurrence: radial, spherical, or hemispherical aggregates composed of thin, acicular crystals. Luster (vitreous to silky), white color, and relatively high hardness (approx. 6) are also helpful in identification. The characteristic hexagonal cross-section of individual crystals is also distinctive, if they are large enough to observe. ## Distinguishing from Similar Minerals Leifite is sometimes confused with other zeolites that form radial aggregates, such as natrolite or mesolite. However, it differs from them by its higher hardness (natrolite and mesolite have a hardness of approx. 5-5.5) and crystallographic system (leifite is trigonal, while natrolite is orthorhombic). Differentiation without specialized tests can be difficult. ## Crystal Forms Leifite crystallizes as elongated, acicular or prismatic crystals with a hexagonal cross-section. It almost always occurs in the form of radial, spherical or hemispherical aggregates. Single, well-formed crystals are extremely rare.
Geological environment
## Genesis Leifite is a hydrothermal mineral, forming in the late stages of crystallization in alkaline pegmatites, especially in nepheline-syenite pegmatites. It forms in cavities and fissures within these rocks, often in association with other rare minerals. ## Mineral Associations This mineral often co-occurs with microcline, aegirine, nepheline, sodalite, eudialyte, polylithionite, as well as other zeolites such as analcime. At Mont Saint-Hilaire, its typical associated minerals include catapleiite, sericite, and rhodochrosite. ## Localities The most important and historically first locality for leifite is the Narssârssuk alkaline complex in Greenland. However, the most well-known and highly prized specimens by collectors, of exceptional quality and size, come from the famous Poudrette quarry at Mont Saint-Hilaire in Quebec, Canada. It is also found in the Khibiny Massif on the Kola Peninsula in Russia.
Rarity
Rare
For collectors
## Quality Criteria The most highly valued leifite specimens are those that form complete, well-defined spheres of radial crystals, set on a contrasting rock matrix. An ideal specimen should have a clean, white color, silky luster, and be free from damage. The size of the aggregates is crucial – the larger and more complete the sphere, the higher the value. Contrast with associated minerals, such as pink rhodochrosite, also significantly enhances visual appeal and price. ## Popular Localities By far the most sought-after leifite specimens by collectors come from the Poudrette quarry at Mont Saint-Hilaire (Quebec, Canada). Specimens from this locality have set the standard for quality for this mineral. Historical specimens from Greenland are rare and primarily of scientific importance.
Care and storage
## Cleaning Leifite specimens, especially delicate, acicular aggregates, should be cleaned with the utmost care. It is best to use compressed air to remove dust. If wet cleaning is necessary, a soft brush and distilled water can be used, avoiding strong pressure that could damage the fragile crystals. ## What to Avoid Avoid contact with acids and strong chemicals, which can react with the mineral. Leifite is sensitive to ultrasonic cleaners, which can cause delicate aggregates to disintegrate. Also avoid sudden temperature changes and prolonged exposure to direct sunlight. ## Storage Due to the fragility of its acicular crystals, leifite specimens should be stored in separate, padded boxes or display cases, away from harder minerals that could scratch or damage them. They should be protected from dust and vibrations.