Manganonordite-(Ce)

Chemical formula: Na₃SrCe₃+Mn₂+Si₆O₁₇

A rare silicate from the nordite group, characterized by manganese and cerium content, found in ultra-alkaline pegmatites.

## Characteristics Manganonordite-(Ce) is a complex silicate of sodium, strontium, cerium, and manganese, belonging to the nordite group. It forms elongated, prismatic crystals that can reach several centimeters in length, although it is most commonly found in granular or radial aggregates. Its crystals are usually poorly formed and intergrown with the rock. ## Physical Properties This mineral is characterized by a hardness of 5-5.5 on the Mohs scale. It has a vitreous luster, and its surfaces can be dull or covered with weathering products. It is a relatively dense mineral, with a specific gravity of 3.5-3.6 g/cm³. It is brittle and exhibits an uneven fracture. ## Colors and Varieties The typical color of manganonordite-(Ce) is brown, reddish-brown to almost black. Thinner fragments or crystal edges may be translucent brown. No color or commercial varieties are distinguished. ## History and Name The name of the mineral refers to its chemical composition and structure. The prefix "Mangano-" indicates the dominance of manganese, "nordite" refers to its belonging to the nordite group, and the suffix "-(Ce)" indicates that cerium is the dominant rare earth element in its composition. The mineral was approved by the IMA in 1998, and its description was published in 1999. It was discovered on Mount Kedykverpakhk in the Lovozero Massif on the Kola Peninsula in Russia. ## Applications Manganonordite-(Ce) has no industrial application. It is solely an object of scientific interest and a valuable acquisition for advanced collectors of rare minerals.

Properties

Mohs hardness: 5-5.5
Luster: Vitreous
Streak: Light brown
Density: 3.5-3.6
Cleavage: Good on {110}, distinct on {010}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Helpful identification features include: brown color, prismatic crystal form, vitreous luster, and characteristic occurrence environment – pegmatites in alkaline massifs. The mineral exhibits weak, reddish fluorescence under ultraviolet light. ## Distinguishing from Similar Minerals It can be confused with other minerals from the nordite group, such as nordite-(Ce) or ferronordite-(Ce). Final distinction requires advanced chemical analysis (e.g., EDS). From other brown minerals of the Lovozero Massif (e.g., lamprophyllite, eudialyte), it is distinguished by crystal form and physical properties, such as hardness and cleavage. ## Crystal Forms Crystals are prismatic, often flattened and elongated along one of the crystallographic axes. It also occurs in granular aggregates, radial aggregates, and as irregular grains intergrown with other minerals.

Geological environment

## Genesis Manganonordite-(Ce) is a magmatic mineral, crystallizing in the late stages of the formation of pegmatites and hydrothermal veins associated with ultra-alkaline nepheline-syenite intrusions (so-called agpaites). ## Mineral Associations It co-occurs with a wide range of rare alkaline minerals. In the Lovozero Massif, these include aegirine, microcline, nepheline, sodalite, lomonosovite, vuonnemite, eudialyte, lamprophyllite, lorenzenite, and sphalerite. In the Khibiny Massif, it is accompanied by natrolite, aegirine, catapleiite, and ancylite-(Ce). ## Localities The most important and best-known occurrences of manganonordite-(Ce) are located on the Kola Peninsula in Russia, within two alkaline massifs: Lovozero (Karnasurt, Kedykverpakhk, Alluaiv mountains) and Khibiny (Mount Eveslogchorr). These are the only confirmed localities from which well-formed specimens originate.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued specimens are those with well-formed, sharp, and undamaged crystals of intense, brown color. Samples where manganonordite-(Ce) is exposed on a rock matrix and contrasts with other minerals, e.g., white microcline, are of great value. Crystal size and the richness of the aggregate also significantly increase collector appeal. ## Popular Localities The vast majority of collector specimens come from the Lovozero Massif on the Kola Peninsula in Russia. Specimens from this region are considered classic and most representative of this mineral.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. In case of heavier soiling, distilled water can be carefully used, and then the specimen should be thoroughly dried. Washing under running water is not recommended. ## What to Avoid The mineral is sensitive to acids, which can damage it. Ultrasonic cleaners, sudden temperature changes, and all types of chemicals should be avoided. Prolonged exposure to direct sunlight is not advisable. ## Storage Manganonordite-(Ce) specimens are best stored in closed collector boxes or display cases to protect them from dust and mechanical damage. Storage in a humid environment should be avoided.

Sources

IMA Mineral List (CNMNC)