Overview

Weloganite is a rare sodium–strontium–zirconium carbonate first discovered in Montréal, Canada, and famed for its distinctive lemon to honey‑yellow crystals. Typically forming sharply faceted, pseudo-hexagonal prisms with steep terminations, crystals range from millimeters to a few centimeters, with occasional larger cabinet examples. Luster is vitreous to slightly resinous, and many specimens show subtle internal zoning. The species is a connoisseur favorite because fine crystals are both visually striking and geochemically unusual—weloganite is one of the few known natural zirconium carbonates. Most collectible material comes from a single historic source, making provenance central to its appeal and value.

Popularity

Weloganite’s reputation rests on scarcity and type-locality prestige. The Francon Quarry (St‑Michel, Montréal), where the species was discovered in the late 1960s, produced a relatively small number of pockets over a limited time; the site has long been inactive. As a result, the supply is finite, and quality pieces have steadily migrated into long-term collections and museums. Prices reflect this: attractive thumbnails and small miniatures are attainable, but well-formed, vivid yellow crystals on aesthetic matrix are uncommon and command strong premiums. Collectors who focus on carbonatites, alkaline environments, or type-locality classics consider weloganite an essential anchor species.

Top Collecting Localities

While weloganite has been reported at very few sites, by far the most important and defining source is its type locality in Montréal.

Francon Quarry, Montréal, Canada

The type and benchmark locality for weloganite, the Francon Quarry (St‑Michel district, Montréal) yielded the classic sharply faceted prisms in shades from pale straw to warm honey yellow. Crystals occur in vugs within carbonate-rich, alkaline-influenced assemblages and are frequently associated with calcite, dolomite, strontianite, and other rare carbonates. The best specimens show glassy luster, crisp edges, and contrasting white to tan matrix that sets off the color. Aesthetic pieces often feature multiple intergrown crystals or isolated, perfectly terminated singles perched in open cavities.

Collectors prize Francon material for:

• Strong color and translucency to local transparency
• Sharp, complete terminations without etching
• Attractive matrix associations that enhance display
• Historic labels documenting pocket/date, which can add value

Production is long past, and surviving fine specimens are limited, making Francon examples the gold standard.

Collector’s Guide

Evaluating Specimen Quality

• Color and Saturation:

  • Desirable weloganite ranges from bright lemon to saturated honey yellow. Strong, even color that reads well in ambient light is ideal.
  • Pale or brownish tones occur; the most coveted pieces balance vividness with clarity.

• Clarity and Luster:

  • Many crystals are translucent with gemmy zones. Clean, bright, vitreous faces elevate a specimen.
  • Dullness or frosting can result from natural etching or aggressive cleaning—high, fresh luster is preferred.

• Crystal Form:

  • Look for sharply developed pseudo-hexagonal prisms with crisp terminations and minimal distortion.
  • Symmetry and completeness matter: undamaged terminations, sharp edges, and distinct face junctions indicate quality.
  • Composition on matrix boosts aesthetics—weloganite perched in open vugs or framed by white calcite/striated strontianite is especially attractive.

• Size:

  • Thumbnails and small miniatures are most common; larger single crystals or clusters become exponentially rarer and more valuable, provided condition and form are strong.

• Condition:

  • Tips and edges are vulnerable. Even tiny nicks can stand out on glossy faces.
  • Watch for cleaning damage: acid etching can leave a matte or pitted surface and reduce desirability.
  • Matrix integrity matters—avoid crumbling bases or unstable vugs that threaten long-term stability.

• Provenance:

  • Detailed labels from the Francon Quarry (pocket information, date, original collector) can meaningfully enhance value.

Detecting Repairs or Treatments

• Repairs/Reattachments:

  • Like many cavity minerals, some weloganite crystals have been reattached to matrix. Inspect junctions with a loupe; look for thin glue lines, misaligned striations, or glossy films at the interface.
  • UV light may reveal adhesive fluorescence on some repairs.

• Over-cleaning and Etching:

  • Aggressive acid cleaning can frost faces and blur edges. Natural luster should be glassy—not uniformly matte.
  • Uneven surface texture, “orange-peel” etching, or chalky-looking patches can indicate chemical overexposure.

• Polishing:

  • Polished terminations are uncommon and generally undesirable. Natural faces show subtle growth features—mirror-flat, perfectly uniform ends may be a red flag.

Care and Storage

Weloganite is a carbonate with modest hardness and should be treated gently.

• Handling:

  • Support matrix pieces with both hands; avoid gripping crystal tips. Use a small amount of museum putty on stands to prevent shifting.

• Cleaning:

  • Prefer dry, soft-brush dusting or a rubber air bulb. If necessary, a brief rinse in distilled water with a drop of mild detergent can be used; avoid soaking and dry promptly.
  • Do not use acids or harsh cleaners—these can etch or dull surfaces and damage associated carbonates.
  • Avoid ultrasonic and steam cleaners.

• Environment:

  • Store in a closed cabinet away from direct sunlight and heat sources. Normal indoor humidity is fine; avoid extremes and rapid temperature swings.
  • LED case lighting is ideal (low UV, low heat).

• Display:

  • Many pieces benefit from gentle, angled lighting to show color and luster. Backlighting can enhance translucency but should not produce heat.

• Transport:

  • Cushion well with soft foam or tissue. Keep crystals from contacting harder specimens that might scratch or chip them.

With careful selection and sensible care, weloganite will retain its vivid color, sharp form, and historical allure for decades—standing out as a quintessential, single-locality classic in any advanced suite of carbonates or Canadian rarities.