How to identify Wavellite

To correctly identify Wavellite (Al3(PO4)2(OH,F)3·5H2O), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically green, yellow-green, white, colorless, brown, or black. Often translucent to opaque.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to pearly on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Often forms radiating, spherical, or hemispherical aggregates of fine acicular crystals, giving a botryoidal or mammillary texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system. Crystals are typically acicular (needle-like) to prismatic, often forming characteristic radiating aggregates, spheres, or hemispheres. Individual crystals are rare and usually very small.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Good on {110} and {010}, but rarely observed due to the fine-grained, radiating habit.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in low-temperature hydrothermal veins, in fissures and cavities of aluminous metamorphic rocks (e.g., phyllites, slates), and as a secondary mineral in phosphate-bearing igneous or sedimentary rocks. Often associated with limonite, variscite, crandallite, and other secondary phosphates.

Key Facts

Hardness

3.5-4 on the Mohs scale

Specific Gravity

2.30-2.37 g/cm³

Crystal System

Orthorhombic

Color

Green, yellow-green, white, colorless, brown, black

Luster

Vitreous to pearly

Transparency

Transparent to translucent to opaque

Fracture

Uneven to subconchoidal

Cleavage

Good on {110} and {010}, but rarely observed due to habit

Composition

Hydrated aluminum phosphate with hydroxyl and fluoride. Al3(PO4)2(OH,F)3·5H2O

Physical characteristics

• Crystal Habit: Typically forms radiating, spherical, or hemispherical aggregates of acicular to prismatic crystals; also botryoidal, mammillary, stalactitic, or massive.
• Cleavage Type: Good on {110} and {010}, but often obscured by the radiating habit.
• Fracture Type: Uneven to subconchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous to pearly.

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