Microlite Mineral Overview

• Mineral name: Microlite
• Mineral class: Oxide (pyrochlore group)
• Chemical formula: (Na,Ca)₂Ta₂O₆(O,OH,F) (variable)
• Crystal system: Isometric (cubic)
• Mohs hardness: 5–5.5
• Color range: Yellow, brown, green, reddish, black
• Luster: Vitreous to resinous
• Streak: White
• Cleavage: Poor
• Fracture: Conchoidal to uneven
• Specific gravity: Approximately 5.6–6.5 (high)
• Transparency: Transparent to opaque
• Common locations: Brazil, Madagascar, United States, Australia
• Uses: Tantalum ore, collector mineral
• Similar minerals: Pyrochlore, columbite-tantalite, wodginite

Naming and Classification

Microlite is a tantalum-rich member of the pyrochlore group, a complex family of oxide minerals.

The name comes from Greek:

• mikros = small
• Referring to its typically small crystal size

It is part of a broader group of minerals important for rare elements, especially:

• Tantalum (Ta)
• Sometimes niobium (Nb)

Physical and Optical Characteristics

Microlite typically occurs as:

• Small octahedral crystals
• Granular or massive aggregates

Well-formed crystals are often:

• Sharp and geometric
• Isometric (cubic symmetry)

Its color varies widely, including:

• Yellow to brown
• Green
• Reddish tones
• Dark or nearly black

The luster ranges from vitreous to resinous, especially in gem-quality specimens.

With a Mohs hardness of 5–5.5, it is moderately hard.

Chemical Composition and Structure

Microlite is composed of:

• Tantalum (Ta) (dominant element)
• Sodium (Na) and calcium (Ca)
• Oxygen (O), hydroxyl (OH), and fluorine (F)

It has a pyrochlore-type structure, characterized by:

• A complex cubic framework
• Variable composition depending on substitutions

This variability is typical of the pyrochlore group.

Formation and Geological Occurrence

Microlite forms in granitic pegmatites, especially those rich in rare elements.

Typical formation environments include:

Rare-Element Pegmatites

• Lithium-, tantalum-, and niobium-rich systems

Late-Stage Magmatic Processes

• Highly evolved magma

It is commonly associated with:

• Spodumene
• Lepidolite
• Quartz
• Columbite-tantalite

These associations indicate rare-element enrichment.

Common Locations

Microlite is found in several important regions:

• Brazil: Major source of tantalum minerals
• Madagascar: Gem-quality specimens
• United States: Pegmatite regions
• Australia: Rare-element deposits

Brazilian and Malagasy specimens are especially notable.

Uses and Practical Significance

Microlite is important for:

Tantalum Production

• Source of tantalum, used in:
  • Electronics (capacitors)
  • Aerospace alloys
  • High-temperature materials

Collector Mineral

• Attractive small crystals
• Interest due to rare-element composition

Similar and Related Minerals

Microlite can resemble:

• Pyrochlore: Niobium-rich counterpart
• Columbite-tantalite: More elongated crystals
• Wodginite: Different structure and composition

Chemical testing is often required for precise identification.

Identification Notes for Collectors

• Look for small, often octahedral crystals
• Note high density (feels heavy for size)
• Observe color variation (yellow to brown common)
• Check moderate hardness (5–5.5)
• Consider association with pegmatite minerals

Microlite is a tantalum-rich oxide mineral, recognized for its role in rare-element pegmatites and importance as a tantalum source, making it both economically valuable and of interest to collectors.