Ferrierite-Na

Chemical formula: (Na,K)₅(Si₃₁Al₅)O₇₂·₁₈H₂O

Ferrierite-Na is a hydrated sodium and potassium silicate from the zeolite group, forming acicular crystals and spherulitic aggregates with a silky luster.

## Characteristics Ferrierite-Na is a mineral from the zeolite group, belonging to the ferrierite subgroup. Chemically, it is a hydrated sodium and potassium aluminosilicate. It forms characteristic, radial or spherulitic aggregates composed of very fine, acicular or bladed crystals. Individual crystals are usually too small to be seen with the naked eye. These aggregates often have a spherical shape and a silky luster, resulting from their fibrous structure. It also occurs as thin layers and crusts on other minerals or in rock fissures. ## Physical Properties This mineral is characterized by relatively low hardness, ranging from 3 to 3.5 on the Mohs scale. Its luster is typically vitreous on crystal faces and silky on the surfaces of fibrous aggregates. It is transparent to translucent. Due to its porous, zeolitic structure, its density is low. ## Colors and Varieties Ferrierite-Na is most often colorless or white. It can also take on creamy, yellowish, pinkish, or orange hues, which are usually caused by the presence of impurities or inclusions of other minerals. No named color varieties or commercial varieties are distinguished. ## History and Name The name "ferrierite" was given in honor of Walter Frederick Ferrier (1865-1951), a Canadian geologist and mining engineer. The suffix "-Na" in the name Ferrierite-Na indicates the dominance of sodium (Na) in the chemical composition of this specific mineral within the ferrierite series. The mineral was described as a distinct species during the redefinition of the ferrierite group by the International Mineralogical Association (IMA). ## Uses Due to its rarity and small crystal size, Ferrierite-Na has no industrial applications. However, it is a valued and sought-after mineral by collectors specializing in zeolites and rare minerals.

Properties

Mohs hardness: 3-3.5
Luster: Vitreous, Silky
Streak: White
Density: 0
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Ferrierite-Na is most easily recognized by its characteristic spherulitic or radial aggregates with a silky luster. Its low hardness (3-3.5 on the Mohs scale) and occurrence in gas vesicles and fissures of volcanic rocks are also important indicators. Identification of individual, microscopic crystals requires advanced analytical methods. ## Distinguishing from Similar Minerals Ferrierite-Na can be confused with other fibrous zeolites, such as natrolite, mesolite, scolecite (natrolite group), or mordenite. However, the natrolite group typically forms more acicular and prismatic crystals. Final differentiation from other rare zeolites, especially from other minerals in the ferrierite subgroup (Ferrierite-Mg, Ferrierite-K), is almost exclusively possible through chemical analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms Crystals are usually strongly flattened, bladed, or acicular. They almost always occur as radial, spherical (spherulitic), or fan-shaped aggregates. Rarely do they form single, well-formed crystals visible to the naked eye.

Geological environment

## Genesis Ferrierite-Na is a low-temperature hydrothermal mineral. It forms as a result of the activity of post-magmatic waters or circulating groundwater, which, by passing through rocks, dissolve and precipitate minerals in gas vesicles, fissures, and vugs. It most commonly forms in voids within volcanic rocks, such as basalts and andesites, as well as in volcanic tuffs. ## Mineral Associations It often co-occurs with other zeolites, such as clinoptilolite, mordenite, heulandite, as well as with quartz (chalcedony, agate) and calcite. ## Localities The most important and classic localities for Ferrierite-Na are in the USA, including the type locality in Altoona, Washington. It is also known from quarries in Oregon (e.g., Neer Road, Goble). Other notable localities include Weitendorf in Styria (Austria) and some sites in Italy and Japan.

Rarity

Rare

For collectors

## Quality Criteria Specimens with well-formed, spherical aggregates (spherulites) with a distinct silky luster are most valued by collectors. Contrast with the rock matrix and the absence of damage to the delicate, fibrous structures are important. Specimens from several localities, such as Altoona, Washington, are particularly sought after due to their historical significance and quality. The size of the spherulites and their aesthetic arrangement on the matrix rock significantly increase the specimen's value. ## Popular Localities Among the most known and valued localities from which collectible Ferrierite-Na specimens originate are Altoona, Washington (USA) and the quarry at Neer Road in Goble, Oregon (USA). Specimens from these locations are considered classic for this mineral.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, compressed air (from a safe distance) can be used, or the specimen can be rinsed in distilled water. Ultrasonic cleaners should be avoided, as they can damage delicate aggregates. ## What to Avoid Contact with acids and strong detergents should be avoided, as they can damage the mineral's structure. Ferrierite-Na, like other zeolites, is sensitive to high temperatures, which can lead to the loss of water from its structure and destruction of crystals. It should be protected from prolonged exposure to direct sunlight. ## Storage Ferrierite-Na specimens are fragile and delicate. It is best to store them 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.