Ferronordite-(La)

Chemical formula: Na<sub>3</sub>SrLa<sup>3+</sup>Fe<sup>2+</sup>Si<sub>6</sub>O<sub>17</sub>

A rare sodium, strontium, lanthanum, and iron silicate, forming tabular crystals of brown color and vitreous luster.

## Characteristics Ferronordite-(La) is a complex silicate from the nordite group, characterized by the presence of lanthanum as the dominant rare earth element. It forms flattened, tabular crystals, often gathered in radial or fan-shaped aggregates. Its color is usually brown to reddish-brown, and on fresh fracture surfaces, it exhibits a strong, vitreous luster. ## Physical Properties This mineral is relatively soft, with a hardness of about 5 on the Mohs scale. It is brittle, and its fracture is uneven. The density is higher than average for silicates, at approximately 3.45 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties Ferronordite-(La) occurs in shades of brown, from light brown through reddish-brown to dark brown. No named varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the presence of iron (Latin: *ferrum*) and its kinship with the older mineral, nordite. The suffix -(La) indicates lanthanum as the dominant rare earth element in its structure. It was first described in 1997 by P. M. Khomyakov and co-workers based on material from the Khibiny Massif in Russia. ## Uses Ferronordite-(La) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and scientists studying the mineralogy of alkaline massifs.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
Light brown
Density
3.45
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Characteristic features of ferronordite-(La) include its tabular crystal habit, brown color, vitreous luster, and occurrence in a specific geological environment. Perfect cleavage in one direction is also an important diagnostic clue. ## Distinguishing from Similar Minerals It can be confused with other brown silicates found in alkaline massifs, such as lamprophyllite, eudialyte, or other minerals from the nordite group. Final distinction requires advanced analytical methods, such as X-ray spectroscopy (EDS/WDS), due to the need to confirm its unique chemical composition. ## Crystal Forms Crystals are usually thin or thick, with a tabular habit, often elongated. They occur as single plates or form radial, fan-shaped, and spherulitic aggregates, growing on other minerals.

Geological environment

## Genesis Ferronordite-(La) is a hydrothermal mineral associated with differentiated alkaline massifs, such as nepheline syenites and their pegmatites. It forms in the late stages of crystallization, in veins and fractures rich in rare earth elements, sodium, and silicon. ## Mineral Associations It most commonly co-occurs with minerals typical of agpaitic pegmatites, such as aegirine, natrolite, microcline, nepheline, lorenzenite, eudialyte, lamprophyllite, and villiaumite. ## Localities The most important and classic localities for this mineral are in Russia, within the Kola Peninsula. These are primarily the alkaline massifs of Khibiny (Koashva Mountain, Nyorkpakhk Mountain) and Lovozero (Karnasurt Mountain, Kedykvyprpakhk Mountain).

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals of intense, reddish-brown color and strong luster are most valued by collectors. Radial aggregates and contrasting associations with other rare minerals, such as white natrolite or pink eudialyte, enhance their attractiveness. Crystal size rarely exceeds a few millimeters, so larger, well-formed specimens are particularly sought after. ## Popular Localities The vast majority of the best collector specimens come from pegmatites in the Khibiny and Lovozero massifs on the Kola Peninsula in Russia. These are the classic and practically only sources of material available on the market.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or paintbrush to remove dust. Compressed air may be used with caution. ## What to Avoid Contact with water, and especially with acids and other chemicals that can react with the mineral and lead to its damage or discoloration, must be strictly avoided. It should not be heated or subjected to ultrasound. Protect from prolonged exposure to sunlight. ## Storage It is recommended to store specimens in stable conditions, in closed boxes or display cases, away from moisture and contaminants. Due to its perfect cleavage, specimens are sensitive to impacts and pressure.

Sources

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