Ferrierite-NH_4_

Chemical formula: (N₃-H₄,Mg₀.₅)₅(Al₅Si₃₁O₇₂)·₂₂H₂O

Ferrierite-NH₄ is a rare mineral from the zeolite group, forming small, colorless or white acicular or lamellar crystals.

## Characteristics Ferrierite-NH₄ is a hydrated aluminosilicate from the zeolite group, in which the ammonium group (NH₄) is the dominant cation. This mineral typically forms very small, acicular or lamellar crystals, which often occur as radial or spherulitic aggregates. Individual crystals are most often colorless or white, with a vitreous or silky luster, which is particularly evident in fibrous aggregates. ## Physical Properties Ferrierite-NH₄ crystals are brittle. Hardness on the Mohs scale is approximately 3-3.5, and density is low, approximately 2.13 g/cm³. The mineral is characterized by a vitreous luster, and in aggregates, a silky luster. It is transparent to translucent. ## Colors and Varieties This mineral is usually colorless or white. No colored or commercial varieties are distinguished. ## History and Name The name "ferrierite" honors the Canadian geologist and mining engineer Walter Frederick Ferrier (1865-1951). The suffix "-NH₄" was added in accordance with the naming rules for minerals of the zeolite group to indicate that the ammonium ion is the dominant extra-framework cation in this particular variety. The mineral was formally described as a new species in 1997. ## Applications Due to its rarity and small crystal size, ferrierite-NH₄ has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or zeolites.

Properties

Mohs hardness: 3-3.5
Luster: Vitreous, Silky
Streak: White
Density: 2.13
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Field identification of ferrierite-NH₄ is practically impossible due to its appearance and rarity. In a collection, it can be recognized by its characteristic radial aggregates composed of small, white or colorless needles. The luster can be silky in fibrous aggregates. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS) to confirm the presence of the ammonium group as the dominant cation. ## Distinguishing from Similar Minerals Ferrierite-NH₄ is visually indistinguishable from other fibrous zeolites, such as natrolite, mesolite, scolecite, or other ferrierite varieties (e.g., -Mg, -K, -Na). It can also be confused with other minerals forming similar aggregates, such as some forms of calcite or aragonite. Final differentiation is possible only through detailed laboratory analysis. ## Crystal Forms This mineral forms elongated, lamellar or acicular crystals, usually of small size. They most often occur as radial, spherical (spherulitic), or fan-shaped aggregates, as well as fibrous masses.

Geological environment

## Genesis Ferrierite-NH₄ is a secondary mineral, formed in low-temperature hydrothermal processes. It forms in cavities and fissures of volcanic rocks, such as basalts, andesites, or tuffs. Its formation is associated with the activity of solutions rich in silica, aluminum, and ammonium ions, which can originate from the decomposition of organic matter in sedimentary rocks. ## Mineral Associations It often co-occurs with other zeolites, such as clinoptilolite, mordenite, dachiardite, as well as with calcite, quartz (chalcedony), and opal. ## Localities The most important and best-documented occurrences of this rare mineral are in Italy, particularly in a quarry near Tiso (Teis) in the Trentino-Alto Adige region. It has also been reported in Windgällen in the canton of Uri, Switzerland, and in the Alto Chapare mine in the Cochabamba department, Bolivia.

Rarity

Very rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, rich spherulitic or radial aggregates that clearly stand out from the matrix rock. The overall aesthetics of the specimen, including the absence of damage to the delicate acicular crystals, is important. Color contrast with the substrate, even though the mineral itself is white or colorless, also enhances visual appeal. ## Popular Localities Specimens from the type locality in Tiso, Italy, are most sought after by collectors specializing in mineral systematics or zeolites.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to the brittleness and delicacy of the aggregates, washing under running water should be avoided. If liquid is necessary, pure distilled water is recommended, followed by very gentle drying, preferably non-contact (e.g., with an air stream). ## What to Avoid Avoid contact with acids and other chemicals that can damage the zeolite structure. The mineral is sensitive to high temperatures, which can cause the loss of crystallization water and destruction of the specimen. Avoid ultrasonic cleaners. ## Storage Ferrierite-NH₄ specimens, especially delicate acicular aggregates, should be stored in sealed display boxes to protect them from dust and mechanical damage. Avoid areas with high humidity or exposure to direct sunlight.