Nordite-(La)

Chemical formula: Na₃Sr₂+La₃+Zn₂+Si₆O₁₇

A rare silicate of sodium, strontium, lanthanum, and zinc, found as brown, prismatic crystals in alkaline pegmatites.

## Characteristics Nordite-(La) is a rare mineral from the nordite group, belonging to the silicate class. It forms elongated, prismatic crystals, often with a rectangular cross-section. It usually occurs as grains embedded in rock or small, acicular aggregates, less frequently as well-formed, single crystals. Its appearance is typically inconspicuous, and specimens are primarily of scientific and collector's value. ## Physical Properties This mineral is characterized by a hardness of 5-5.5 on the Mohs scale. It has a vitreous luster, and on fracture surfaces, it can also be resinous. It is brittle, and its density is approximately 3.6-3.7 g/cm³. It is a translucent mineral, and in thicker sections, it is opaque. ## Colors and Varieties Nordite-(La) ranges in color from yellowish-brown, through reddish-brown, to almost black. The color change depends on minor impurities of other elements. The name Nordite-(La) indicates lanthanum as the dominant rare-earth element in its structure, distinguishing it from other minerals in this group, such as nordite-(Ce). ## History and Name The name "nordite" comes from the place of the initial discovery of a mineral from this group on the Kola Peninsula in Russia (the word "nord" means "north"). The suffix "-(La)" was added according to mineral nomenclature rules to indicate lanthanum as the dominant rare-earth element in this specific mineral. It was formally described as a distinct mineral species in 1982. ## Applications Due to its rarity, nordite-(La) has no industrial applications. It is solely an object of scientific interest and a valued acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness: 5 - 5.5
Luster: Vitreous to Resinous
Streak: White to pale yellow
Density: 3.6 - 3.7
Cleavage: Good on {100} and {010}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Helpful features for identifying nordite-(La) include its prismatic crystal habit, brown color, vitreous luster, and hardness. However, the key is its occurrence environment – nepheline-syenite pegmatites – and associated minerals. ## Distinguishing from Similar Minerals Nordite-(La) can be confused with other brown silicates found in the same environment, such as lamprophyllite (which has a different habit and perfect cleavage in one direction), aegirine, or some varieties of eudialyte. Definitive differentiation usually requires advanced studies, including chemical analysis (EDS). ## Crystal Forms Nordite-(La) crystals are prismatic, often elongated along one axis. They occur as single crystals embedded in rock, as well as in radial or tangled aggregates.

Geological environment

## Genesis Nordite-(La) is a magmatic mineral, crystallizing in the late stages from residual, rare-earth and alkali-rich solutions within nepheline-syenite pegmatites (so-called agpaitic pegmatites). ## Mineral Associations This mineral co-occurs with other rare minerals typical of alkaline pegmatites, such as eudialyte, lorenzenite, lamprophyllite, rinkite, as well as with more common rock-forming minerals: nepheline, microcline, and aegirine. ## Localities The most important and classic occurrences of nordite-(La) are the alkaline massifs of the Kola Peninsula in Russia, primarily the Lovozero Massif (Mount Alluaiw, Karnasurt) and, to a lesser extent, the Khibiny Massif.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp, and undamaged crystals of intense brown color are most valued by collectors. Crystal size is of great importance – those exceeding a centimeter in length are already rare. Aesthetic compositions of nordite-(La) with other rare minerals, such as pink eudialyte or black aegirine, are also highly regarded. ## Popular Localities By far the most sought-after specimens come from the Lovozero Massif on the Kola Peninsula in Russia. This is the type locality for this mineral, from which the best-known crystals originate.

Care and storage

## Cleaning Nordite-(La) specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, it can be rinsed with distilled water and then thoroughly dried. Strong rubbing should be avoided. ## What to Avoid This mineral is sensitive to strong acids. It should not be cleaned in ultrasonic cleaners or exposed to sudden temperature changes, which could cause cracks. ## Storage It is recommended to store specimens in closed boxes or display cases to protect them from dust and mechanical damage. It does not require special conditions regarding humidity or lighting, but prolonged exposure to direct sunlight should be avoided.

Sources

IMA Mineral List (CNMNC)