Cavansite Mineral Overview

Mineral name: Cavansite
Mineral class: Silicate (phyllosilicate)

Known Facts

• Chemical formula: Ca(VO)Si₄O₁₀·4H₂O
• Crystal system: Orthorhombic
• Mohs hardness: 3–4
• Color range: Deep blue, azure blue, blue-green
• Luster: Vitreous
• Streak: Pale blue to white
• Cleavage: Perfect in one direction
• Fracture: Uneven
• Specific gravity: Approximately 2.2–2.4
• Common locations: India, United States (Oregon), Brazil
• Uses: Collector specimens
• Similar minerals: Pentagonite, azurite, blue apophyllite

Physical and Optical Characteristics

Cavansite is best known for its intense blue color and striking crystal habit.

It typically forms:

• Radiating spherical clusters
• Rosette-like aggregates
• Acicular (needle-like) crystals

Crystals are usually transparent to translucent, and their radial growth produces visually dramatic specimens.

The color is typically bright azure blue, sometimes with slight greenish tones. This vivid coloration makes cavansite highly recognizable.

The luster is vitreous, and cleavage is perfect in one direction, though it is not always easily visible due to crystal form.

Chemical Composition and Structure

Cavansite has the formula:

• Ca(VO)Si₄O₁₀·4H₂O

It is a hydrated calcium vanadium silicate, containing:

• Calcium (Ca)
• Vanadium (V⁴⁺) — responsible for the blue color
• Silicate sheets (Si₄O₁₀)
• Water (H₂O)

Structurally, it is a phyllosilicate, meaning:

• It has sheet-like silicate structures
• Water molecules are incorporated within the structure

Formation and Geological Occurrence

Cavansite forms in low-temperature hydrothermal environments, particularly:

• Basalt cavities (vesicles)
• Secondary mineral deposits in volcanic rocks

Typical formation conditions include:

• Circulation of vanadium-bearing fluids
• Deposition in open cavities within basalt

It is commonly associated with:

• Stilbite
• Heulandite
• Apophyllite
• Other zeolite minerals

These associations are characteristic of zeolite-rich basalt environments.

Common Locations

Notable occurrences of Cavansite include:

• India: Maharashtra (Deccan Traps; most famous and abundant source)
• United States: Oregon
• Brazil: Limited occurrences

Indian specimens are especially prized for their bright color and well-formed spherical aggregates.

Uses and Practical Significance

Cavansite has no industrial applications. Its importance lies in:

• Mineral collecting: Highly valued for its vivid color and unique crystal habit
• Display specimens: Often associated with white zeolites, creating strong visual contrast

It is considered a classic collector mineral.

Similar and Related Minerals

Cavansite may be confused with:

• Pentagonite: Chemically identical but different crystal habit (more prismatic, not spherical)
• Azurite: Darker blue and typically forms different crystal shapes
• Blue apophyllite: Different structure and cleavage

Distinguishing features include:

• Bright blue radiating spheres
• Association with zeolite minerals
• Occurrence in basalt cavities

Identification Notes for Collectors

• Look for intense blue spherical clusters in basalt cavities
• Note association with stilbite and apophyllite
• Check for softness (3–4) and delicate crystal structure
• Observe radiating acicular crystals forming rosettes
• Handle carefully due to fragility

Cavansite is a visually striking vanadium-bearing silicate, recognized for its vivid blue color and radiating crystal clusters, and is highly prized by collectors of zeolite minerals.