Overview

Cavansite is a vivid blue, hydrated calcium vanadyl silicate, Ca(VO)Si4O10·4H2O, famed for its brilliant color and elegant rosette crystal clusters. Typically forming as radiating sprays and spherical to hemispherical “pom‑pom” aggregates of slender bladed crystals, cavansite occurs in basaltic amygdales of the Deccan Traps and other zeolite-rich environments. Its electric royal‑blue hue contrasts spectacularly against pale host minerals—especially white or peach stilbite and heulandite—creating some of the most eye-catching display pieces in modern mineral collecting.

Crystals are usually millimeter-scale blades, but rosettes can reach several centimeters across in the best Indian specimens. A classic companion is pentagonite, a dimorph with the same chemistry but different structure and habit; pentagonite’s spiky, starburst sprays can occur on the same matrix as cavansite, and both share the same intense blue color. Cavansite is relatively soft and brittle (roughly Mohs 3–4), so undamaged clusters, well-isolated on attractive matrix, are particularly prized.

Popularity

Once an extreme rarity known mainly from the type locality near Owyhee Dam, Oregon, cavansite became an international sensation when the Maharashtra (Pune District) quarry fields in India began producing in quantity during the 1990s–2000s. The best Indian finds—deep blue, lustrous rosettes on snowy stilbite or heulandite—instantly elevated the species to centerpiece status for contemporary collections. Production has been sporadic and subject to quarry closures and development pressures; as access has diminished, top-quality, unrepaired, well-composed matrix pieces have become harder to obtain and values have risen accordingly.

Because cavansite combines unmistakable color, pleasing geometry, and strong contrast, it appeals to both new and advanced collectors. Beginners can find smaller rosettes at approachable prices, while advanced collectors compete for large, isolated “flowers” with perfect luster on dramatic, undamaged matrix—a recipe for cabinet-level showpieces.

Top Collecting Localities

Wagholi Quarries, Pune District, India

The Wagholi quarry complex produced the world’s finest cavansite specimens. Classic pieces show intensely saturated royal-blue rosettes—often 1–3 cm, rarely larger—perched on white to pale-peach stilbite or heulandite. The best are exquisitely isolated, with mirror-bright luster and symmetric radiating form. Variations include hemispherical “pom-poms,” flattened rosettes, and aesthetic groupings of several rosettes of differing sizes. Associations with apophyllite, mordenite, and occasionally pentagonite add interest and contrast.

Collectors favor Wagholi for its combination of color, size, and composition: a single, sharply isolated, deep-blue rosette on clean white matrix is the archetype. Because pocket extraction often broke clusters, expertly repaired specimens exist and should be disclosed; truly unrepaired pieces, excellent from all angles, command strong premiums. As quarry activity has waned, availability of top pieces has diminished, cementing Wagholi’s status as the definitive cavansite source.

Collector’s Guide

Evaluating Specimen Quality

• Color and Saturation:

  • Seek the richest royal to electric blue; saturation should be strong without dull gray or green overtones.
  • Uniform color across the rosette is best. Uneven color or pale, chalky zones lowers appeal.
  • Backlighting is not essential—top cavansite “pops” in ambient light.

• Crystal Form and Symmetry:

  • Ideal cavansite forms crisp, radial rosettes or hemispheres composed of tightly packed, lustrous blades.
  • Symmetry matters: balanced, circular rosettes with a neat “hub-and-spoke” look are preferred over ragged or incomplete aggregates.
  • Size counts within reason: 1–3 cm rosettes are common; larger, sharp, undamaged rosettes are scarce and highly coveted.

• Luster and Surface Quality:

  • Look for vivid, glassy reflections on individual blades; dull or frosted surfaces reduce sparkle.
  • Avoid matte, powdery-looking clusters unless justified by a rare association or historic label.

• Matrix and Composition:

  • Strong contrast drives desirability—e.g., a single, isolated blue rosette on clean white stilbite/heulandite.
  • Composition and balance are key: one hero rosette, well-placed, with minor satellites can be more aesthetic than a crowded cluster.
  • Apophyllite, stilbite “bowties,” and delicate heulandite sheaves can elevate aesthetics if they don’t overwhelm the cavansite.

• Condition:

  • Cavansite is brittle; look closely for bruises (whitish spots) or missing segments along the rosette edge.
  • Check the perimeter of the rosette and the contact with matrix for chips and extraction damage.
  • Because many pieces were repaired, disclosure is standard. A single, non-distracting repair on a cabinet specimen may be acceptable; multiple or messy repairs are less desirable.

• Cavansite vs. Pentagonite:

  • Cavansite typically forms rounded rosettes/hemispheres of blades; pentagonite forms spiky, stellate sprays with a more pronounced “starburst” appearance.
  • Both share the same color; mixed cavansite–pentagonite association on one specimen can be especially desirable when clear and undamaged.

Detecting Repairs or Treatments

• Common Repairs:

  • Reattached rosettes: Examine the rosette–matrix interface under 10x magnification. Glue lines can appear as glossy, transparent films or slightly discolored halos. Some epoxies fluoresce under longwave UV.
  • Composite matrices: Watch for matrix sections that don’t geologically match (texture, mineral association) or show consistent glue seams.
  • Reassembled rosettes: Look for straight junctions or slight misalignments within a cluster.

• Cleaners and Alterations:

  • Matrix is often cleaned with mild acids to remove calcite or iron staining; over-etching can leave a granular or roughened surface on the matrix.
  • True dyeing is uncommon; intensely vivid blue is natural for cavansite. If color looks “painted on,” inspect closely for residues in crevices.
  • Coatings to enhance luster are undesirable; a uniform plastic-like sheen in protected areas can indicate a coating.

• Best Practice:

  • Buy from reputable dealers; ask directly about repairs or stabilization.
  • Accept that careful, disclosed repairs are common in larger Indian matrix pieces; price should reflect the number and visibility of repairs.

Care and Storage

• Handling:

  • Cavansite is soft/brittle. Always handle matrix, not the rosettes. Use both hands with larger specimens.
  • Avoid vibrations and jolts; rosettes can shear off at the base.

• Cleaning:

  • Dust gently with a soft brush or air bulb. If necessary, use lukewarm water with a drop of mild soap and a very soft brush, avoiding aggressive scrubbing on the rosettes.
  • Rinse and air-dry thoroughly. Do not use ultrasonic or steam cleaners; they can shatter clusters or break repairs.
  • Avoid strong acids near cavansite rosettes; reserve any chemical cleaning for experienced preparators and test first on inconspicuous areas of matrix.

• Light, Heat, and Environment:

  • Colors are generally stable in normal display. Avoid prolonged direct sunlight and heat sources that can dehydrate or weaken adhesives.
  • Keep temperature stable; avoid hot case lights directly over the rosettes. LED lighting is ideal.

• Storage and Display:

  • Display in a cabinet with minimal air currents and dust. Secure with a tiny amount of museum putty on the matrix (never on the rosette).
  • For storage, use padded, individual boxes. Keep away from harder specimens that could shed fragments or scratch softer matrix minerals (stilbite/heulandite).
  • Periodically inspect for loosening at repaired joins or developing dust films in crevices.

By focusing on saturated color, crisp radial symmetry, strong matrix contrast, and pristine condition—while remaining vigilant for repairs—you can select cavansites that capture the species’ trademark “electric blue bloom” and hold enduring appeal in any collection.