Meliphanite
Chemical formula: Ca₄(Na,Ca)₄Be₄AlSi₇O₂₄(F,O)₄
Meliphanite is a rare beryllium, calcium, and sodium silicate, forming tabular crystals with a vitreous or pearly luster, prized by collectors.
Properties
- Mohs hardness
- 5-5.5
- Color
- yellow, yellowish red, nearly colourless
- Luster
- Vitreous, Pearly
- Streak
- white
- Density
- 0
- Cleavage
- Perfect on {001}
- Fracture
- Conchoidal
- Transparency
- Transparent,Translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Key diagnostic features of meliphanite include its tetragonal, tabular crystal habit, yellow color, vitreous-pearly luster, and perfect cleavage in one direction. Its occurrence in nepheline syenites and pegmatites is also characteristic. ## Distinguishing from Similar Minerals Meliphanite is sometimes confused with other minerals from the melilite group, such as leucophanite or gehlenite. It usually differs from leucophanite by the absence of twinning and slightly different optical properties. From gehlenite and åkermanite, it is distinguished by the presence of beryllium in its chemical composition, which requires advanced analysis. In rare cases, it may resemble pale mica, but it differs significantly from mica by the much lower elasticity of its lamellae. ## Crystal Forms Meliphanite crystals are typically thin- to thick-tabular, with a square or octagonal cross-section. They often form irregular granular or blastic aggregates within the host rock. Massive forms are less common.
Geological environment
## Genesis Meliphanite is a mineral of magmatic origin. It forms in the late stages of crystallization in nepheline syenites and associated pegmatites, which are silica-poor and alkali-rich (sodium and potassium) rocks. ## Mineral Associations This mineral often co-occurs with other rare minerals typical of such an environment, such as eudialyte, aegirine, nepheline, microcline, leucophanite, astrophyllite, lorenzenite, and catapleiite. ## Localities The most important and classic locality, from which the best meliphanite specimens originate, is the Langesundsfjorden intrusive complex in the Vestfold region of Norway. Significant occurrences have also been reported on the Kola Peninsula in Russia (Khibiny and Lovozero massifs) and at Mont Saint-Hilaire in Quebec, Canada.
Rarity
Rare
For collectors
## Quality Criteria The most desirable specimens for collectors are those with sharply terminated, well-formed, tabular crystals of an intense, honey-yellow color. Transparent crystals, free from cracks and inclusions, are also highly valued. The attractiveness of a specimen is enhanced by a contrasting host rock background, such as dark aegirine or white nepheline, and association with other rare minerals. ## Popular Localities By far the most prized and classic meliphanite specimens come from the Langesundsfjorden area in Norway. Specimens from Mont Saint-Hilaire in Canada and the Kola Peninsula in Russia are also sought after, although they often have a slightly different habit or color.
Care and storage
## Cleaning Meliphanite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, a damp cloth with distilled water can be used, and the specimen should then be immediately dried. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is sensitive to acids, which can damage it. Contact with household and laboratory chemicals should be avoided. It should not be heated or exposed to sudden temperature changes. Prolonged exposure to intense sunlight may potentially cause color fading. ## Storage Meliphanite is relatively soft and brittle, so it should be stored separately in a padded box to prevent scratching by harder minerals. It is best displayed in a closed cabinet, protected from dust and mechanical damage.