Wavellite Mineral Overview

• Mineral name: Wavellite
• Mineral class: Phosphate
• Chemical formula: Al₃(PO₄)₂(OH,F)₃·5H₂O
• Crystal system: Orthorhombic
• Mohs hardness: 3.5–4
• Color range: White, green, yellow, blue-green, brown (green shades are most common)
• Luster: Vitreous to silky
• Streak: White
• Cleavage: Perfect in one direction (rarely observed due to habit)
• Fracture: Uneven to splintery
• Specific gravity: Approximately 2.3–2.4
• Transparency: Translucent to opaque
• Common locations: United States, United Kingdom, Brazil, Germany, Australia
• Uses: Collector mineral, ornamental stone (limited)
• Similar minerals: Wardite, variscite, turquoise

Physical and Optical Characteristics

Wavellite is most recognizable by its radiating spherical aggregates, often referred to as botryoidal or globular formations. These rounded clusters are composed of fine, needle-like crystals that radiate outward from a central point, creating a distinctive starburst or fibrous appearance when cut or broken.

The mineral commonly displays shades of green, ranging from pale yellow-green to deep green. White and yellow varieties also occur, and less commonly bluish tones may be present. Color variations are influenced by trace elements and environmental conditions during formation.

Its luster varies depending on the surface:

• Outer surfaces: Vitreous to slightly dull
• Fibrous interiors: Silky, especially when exposed

With a Mohs hardness of 3.5 to 4, wavellite is relatively soft and can be scratched easily. The fibrous structure gives it a somewhat brittle nature, and fracture surfaces are typically uneven or splintery.

Chemical Composition and Structure

Wavellite is a hydrated aluminum phosphate containing hydroxyl (OH), fluorine (F), and water molecules. The relative proportion of hydroxyl and fluorine can vary, which is reflected in the formula.

Its structure consists of chains and clusters of aluminum octahedra linked to phosphate groups, forming a framework that accommodates water molecules. This hydration contributes to its relatively low hardness and density.

The fibrous crystal habit is a direct result of how the mineral grows, with elongated crystals radiating outward during formation.

Formation and Geological Occurrence

Wavellite forms as a secondary mineral in aluminum-rich, phosphate-bearing environments. It typically develops through the alteration of primary minerals under low-temperature conditions.

Common formation settings include:

• Weathered zones of aluminum-rich rocks
• Phosphate deposits
• Clay-rich sediments and soils

It is often found in:

• Fractures and cavities in host rock
• Coatings on rock surfaces
• Nodular or botryoidal masses

Associated minerals frequently include:

• Variscite
• Wardite
• Crandallite group minerals
• Kaolinite

These associations reflect environments rich in aluminum and phosphorus, often influenced by groundwater activity.

Common Locations

Wavellite is found in several well-known localities worldwide:

• United States: Arkansas (notably Mount Ida area), Pennsylvania
• United Kingdom: Devon and Cornwall (historic localities)
• Brazil: Produces well-formed specimens
• Germany: Classic European occurrences
• Australia: Various phosphate-bearing regions

Arkansas is particularly famous for producing high-quality wavellite specimens with well-developed radial structures.

Uses and Practical Significance

Wavellite has limited industrial use but is valued for:

• Mineral collecting: Highly sought after due to its distinctive spherical and radiating forms
• Ornamental use: Occasionally cut and polished for decorative purposes, especially when showing attractive internal patterns

Because of its softness and fibrous structure, it is not suitable for most jewelry applications.

Similar and Related Minerals

Wavellite may be confused with other phosphate minerals, particularly those that occur in similar environments.

Common similar minerals include:

• Wardite: Forms crystals rather than radiating spheres
• Variscite: Typically massive and more uniformly colored, often used as a gemstone
• Turquoise: Blue to green and more compact, without fibrous radial structure
• Crandallite group minerals: May appear similar in earthy or nodular forms

The radiating fibrous structure of wavellite is usually the most reliable visual distinction.

Identification Notes for Collectors

• Look for spherical or hemispherical clusters with radiating internal structure
• Check for green, white, or yellow coloration
• Observe silky luster on broken or cut surfaces
• Note relatively low hardness (scratches easily)
• Consider geological context—often found in phosphate-rich, weathered environments

Wavellite is a distinctive phosphate mineral that is most easily identified by its radial, fibrous growth habit and characteristic spherical formations.