Bastnäsite Mineral Overview

Mineral name: Bastnäsite (group minerals: Bastnäsite-(Ce), -(La), -(Y))
Mineral class: Carbonate (carbonate–fluoride)

Known Facts

• Chemical formula: (Ce,La,Y)CO₃F (varies by dominant rare earth element)
• Crystal system: Hexagonal
• Mohs hardness: 4–4.5
• Color range: Yellow, brown, reddish-brown, orange, honey-yellow
• Luster: Vitreous to resinous
• Streak: White
• Cleavage: Poor
• Fracture: Uneven to subconchoidal
• Specific gravity: Approximately 4.9–5.2
• Common locations: China, United States, Sweden, Madagascar
• Uses: Major ore of rare earth elements (REEs), collector specimens
• Similar minerals: Monazite, parisite, synchysite

Definition and Classification

Bastnäsite refers to a group of rare earth carbonate minerals, typically classified by the dominant rare earth element:

• Bastnäsite-(Ce) (cerium-dominant, most common)
• Bastnäsite-(La)
• Bastnäsite-(Y)

It is one of the most important rare earth element (REE) minerals.

Physical and Optical Characteristics

Bastnäsite typically occurs as:

• Massive or granular aggregates
• Tabular or prismatic crystals
• Earthy or compact forms

Crystals are usually opaque to translucent, though thin edges may be translucent.

Color is commonly:

• Yellow to brown or reddish-brown
• Sometimes orange or honey-colored

The luster is vitreous to resinous, especially on fresh surfaces.

A notable feature is its high density compared to most carbonates, due to the presence of rare earth elements.

Chemical Composition and Structure

Bastnäsite has the general formula:

• (Ce,La,Y)CO₃F

It is a rare earth carbonate fluoride, containing:

• Rare earth elements (REEs) such as cerium, lanthanum, and yttrium
• Carbonate groups (CO₃²⁻)
• Fluorine (F)

The exact composition varies depending on the dominant REE, which determines the mineral suffix.

It is closely related to:

• Parisite: Contains calcium in addition to REEs
• Synchysite: More complex carbonate–fluoride composition

Formation and Geological Occurrence

Bastnäsite forms in rare-element-rich environments, particularly:

Carbonatites

• One of the most important sources
• Igneous rocks rich in carbonate minerals

Hydrothermal veins

• Associated with:
  • Fluorite
  • Quartz
  • Barite

Alkaline igneous complexes

• Forms in silica-poor, REE-rich systems

It is commonly associated with:

• Monazite
• Fluorite
• Calcite
• Barite

These environments are enriched in rare earth elements.

Common Locations

Major occurrences of Bastnäsite include:

• China: Bayan Obo deposit (world’s largest REE source)
• United States: Mountain Pass, California
• Sweden: Bastnäs (type locality)
• Madagascar: Pegmatite and carbonatite deposits

China is currently the dominant global producer.

Uses and Practical Significance

Bastnäsite is extremely important economically:

Rare earth element source

• Major source of:
  • Cerium, lanthanum, neodymium, and other REEs

Used in:

• Electronics
• Magnets (e.g., neodymium magnets)
• Catalysts
• Renewable energy technologies

Collecting

• Some specimens are valued for color and rarity

Similar and Related Minerals

Bastnäsite may be confused with:

• Monazite: Phosphate mineral, typically heavier and different chemistry
• Parisite: Similar appearance but contains calcium
• Synchysite: More complex carbonate–fluoride mineral

Distinguishing features include:

• Carbonate + fluorine composition
• Occurrence in carbonatites and REE deposits
• Yellow to brown coloration

Identification Notes for Collectors

• Look for yellow to brown REE minerals in carbonatite or alkaline environments
• Note association with fluorite and barite
• Check for moderate hardness (4–4.5) and resinous luster
• Consider high density compared to typical carbonates
• Use laboratory analysis to confirm REE composition

Bastnäsite is a key rare earth carbonate mineral, recognized for its critical role as a primary source of rare earth elements and its occurrence in specialized igneous environments, making it both economically vital and scientifically important.