Aminoffite
Chemical formula: Ca<sub>3</sub>(BeOH)<sub>2</sub>Si<sub>3</sub>O<sub>10</sub>
Aminoffite is a rare mineral from the silicate group, forming characteristic, tetrahedral crystals with a vitreous luster, found in skarns.
Properties
- Mohs hardness
- 5.5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.0
- Cleavage
- Distinct on {001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification A characteristic feature of aminoffite is its crystallographic form – typical are pyramidal, tetragonal crystals resembling pyramids. Vitreous luster, light color (colorless, white, pale yellow), and occurrence in a specific geological environment (skarns) are key indicators. ## Distinguishing from Similar Minerals It can be confused with other colorless or white minerals with pyramidal crystals, such as apophyllite or scheelite. It differs from apophyllite by the lack of perfect cleavage and pearly luster on the base. It differs from scheelite by its significantly lower density (scheelite is very heavy) and often weaker fluorescence under UV light. ## Crystal Forms Aminoffite crystals have a tetragonal-pyramidal habit, often resembling a tetrahedron. They usually occur as single, overgrown crystals on a rock matrix.
Geological environment
## Genesis Aminoffite is a metamorphic mineral. It forms in skarns, which are carbonate rocks (e.g., limestones) that have undergone alteration due to high temperature and the action of hydrothermal solutions originating from intruding granitic magmas. It is a product of contact metasomatism. ## Mineral Associations This mineral co-occurs with other minerals typical of skarns, such as vesuvianite, garnet (andradite), diopside, calcite, and also with other beryllium minerals, e.g., meliphanite. ## Localities The most important and classic locality for aminoffite is the Långban mine in the Filipstad region, Värmland province, Sweden. This is its type locality, from which the best-known specimens originate. Outside Sweden, its presence has been noted in the Jakobsberg mine, also in the Nordmark district.
Rarity
Very rare
For collectors
## Quality Criteria The most valued aminoffite specimens are those with sharp, well-formed, and undamaged crystals with a distinct, pyramidal shape. Transparency and lack of inclusions are highly prized. The contrasting placement of white or colorless crystals on a darker rock matrix significantly enhances the visual appeal and value of the specimen. Crystal size is also an important factor, with specimens exceeding 5 mm considered exceptional. ## Popular Localities The only source of valuable collector-grade aminoffite specimens is the historic Långban mine in Sweden. Material from this locality is considered classic and most sought after by collectors specializing in rare minerals or skarn minerals.
Care and storage
## Cleaning Aminoffite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Always allow the specimen to dry completely at room temperature. ## What to Avoid Avoid contact with acids and other aggressive chemicals, which can damage the crystal surface. The mineral is brittle, so it must be protected from impacts and falls. It should not be heated or exposed to sudden temperature changes. ## Storage Aminoffite specimens are best stored in separate, padded display boxes to prevent scratches and mechanical damage. Protect from dust and moisture. It can be displayed in closed showcases.