Cordylite-(La)
Chemical formula: NaCaBa₂La₃Sr(CO₃)₈F₂
Cordylite-(La) is a rare mineral from the carbonate group, distinguished by its high lanthanum content and complex chemical composition.
Properties
- Mohs hardness
- 4
- Color
- Colorless, honey-yellow, or pinkish yellow
- Luster
- Vitreous, Resinous
- Streak
- White
- Density
- 4.34
- Cleavage
- on {0001}
- Fracture
- Irregular/Uneven,Conchoidal
- Transparency
- Translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Cordylite-(La) can be identified by its hexagonal, tabular crystals, yellowish color, and vitreous or resinous luster. A key diagnostic feature is its violent reaction with hydrochloric acid, which confirms its nature as a carbonate. High density is also helpful in identification. ## Distinguishing from Similar Minerals It can be confused with other rare-earth carbonates, such as Cordylite-(Ce) or Ancylite. Distinguishing these minerals without advanced chemical analysis (e.g., EDS) is practically impossible, as they have very similar physical properties and often co-occur. They differ in the dominant rare-earth element in their structure. ## Crystal Forms Crystals are usually small, tabular or short-prismatic, consistent with hexagonal symmetry. They often form rosette-like aggregates or granular aggregates embedded in the host rock.
Geological environment
## Genesis Cordylite-(La) is a hydrothermal mineral, associated with late stages of crystallization in alkaline igneous complexes, such as nepheline syenites and carbonatites. It forms in veins and mineral druses cutting through these rocks. ## Mineral Associations It often co-occurs with other rare-earth minerals and minerals typical of alkaline environments. The most common associations include: Cordylite-(Ce), Eudialyte, Aegirine, Nepheline, Microcline, Albite, Natrolite, as well as rarer minerals like Steenstrupine-(Ce) or Rinkite. ## Localities The most important and classic locality for this mineral is the Ilímaussaq intrusive complex in southern Greenland. It is also known from the Kola Peninsula in Russia (Khibiny and Lovozero massifs) and from the Mont Saint-Hilaire complex in Quebec, Canada. These are the main localities providing material for research and collections.
Rarity
Very rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and undamaged crystals of a distinct yellow color. Crystals embedded in a contrasting matrix, for example, on white Albite or dark Aegirine, are particularly sought after. Crystal size is a key factor – specimens with crystals exceeding a few millimeters are already considered exceptional. ## Popular Localities By far the most desirable specimens come from Mont Saint-Hilaire in Canada, which is famous for producing the world's best-formed crystals of this mineral. Classic specimens from Greenland and the Kola Peninsula are also valued, although they often appear as less spectacular aggregates or embedded grains.
Care and storage
## Cleaning Cordylite-(La) specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its reactivity with acids, all chemical cleaning agents should be avoided. If liquid is necessary, distilled water is recommended, followed by thorough drying of the specimen. ## What to Avoid The mineral is sensitive to acids, which cause it to effervesce violently and decompose. It should be protected from contact with household and laboratory chemicals. It should also not be heated or exposed to sudden temperature changes. ## Storage Collector's specimens of Cordylite-(La), due to their rarity and brittleness, should be stored in separate, padded boxes or display cases, away from harder minerals that could scratch them. Stable conditions without high humidity and direct sunlight should be ensured.