Overview

Selenite is the transparent, crystalline variety of gypsum (CaSO4·2H2O), celebrated for its water-clear “windowpane” crystals, distinctive fishtail (swallowtail) twins, and ethereal luster. It forms in low-temperature evaporite environments, geodes, karst cavities, and salt flats. While gypsum is widespread, fine selenite can be remarkably aesthetic: colorless to honey-toned blades and prisms with silky to glassy sheen, often perfectly limpid. Signature habits include broad tabular plates, featherlike fishtail twins, spear-shaped prisms, and sand-included “hourglass” crystals. In arid regions, selenite aggregates with sand into famous “desert roses,” coveted for their sculptural symmetry. The species ranges from affordable cabinet pieces to iconic, museum-scale crystals—none more legendary than the giant selenites of Naica, Mexico. Selenite’s softness and perfect cleavage demand careful handling, but its quiet elegance and variety make it a staple of both beginner and advanced mineral collections.

Popularity

Selenite is popular for three reasons: visual drama, availability, and variety. Even modest specimens can be striking—paper-thin windows with mirror luster or crisp fishtail twins that look “drawn with a ruler.” Iconic occurrences keep collector interest high: Naica’s gargantuan crystals are world-famous; Spain produces classic water-clear blades; Oklahoma’s Great Salt Plains yields “hourglass” sand inclusions unique to that locality; and Tunisia’s Zaghouan area is synonymous with textbook desert roses. Prices span from inexpensive desert roses and small plates to higher-end fishtail twins on matrix or large, perfectly undamaged plates. Because selenite is soft and cleaves easily, pristine, well-terminated crystals—especially in displayable arrangements—command a premium. The species’ broad reach means nearly every collection can include a good selenite, yet the quest for top-tier clarity, size, and form remains compelling for connoisseurs.

Top Collecting Localities

Below are renowned sources that have set the standards for form, variety, and aesthetics in selenite collecting. Each subsection highlights what collectors prize from that locality.

Collector’s Guide

Evaluating Specimen Quality

• Clarity and Luster:

  • For plate-like crystals, collectors favor high transparency and a bright, glassy to silky luster. Water-clear “windows” with minimal veils are most desirable.
  • Slight warmth (honey tones) can enhance aesthetics, but milky cloudiness or scratches reduce impact.
  • Satin-spar fibrous pieces are valued more for sheen and shape than transparency.

• Form and Habit:

  • Fishtail (swallowtail) twins are classic and sought-after; look for crisp twin junctions and intact tips.
  • Broad tabular plates should have sharp edges and clean terminations; very thin “windows” are impressive but fragile.
  • Hourglass selenite (Oklahoma) is judged by the clarity and symmetry of the hourglass sand inclusion and sharp, undamaged faces.
  • Desert roses should be complete, symmetric rosettes with well-defined blades and minimal broken petals.
  • Matrix increases desirability if the composition is balanced and secure; however, many selenites are naturally loose due to cleavage.

• Size and Proportions:

  • Selenite can reach impressive size; larger clear plates with minimal damage are uncommon and command premiums.
  • For twins and roses, balanced proportions and a strong silhouette are key to visual appeal.

• Condition:

  • Selenite is very soft (Mohs ~2) with perfect cleavage; even tiny edge nicks are noticeable. Inspect terminations carefully under good light.
  • Avoid specimens with obvious scratches or “frosted” abrasion unless the piece is otherwise exceptional (e.g., rare form or significant provenance).

• Color:

  • Most collectible selenite is colorless to pale honey. Even, attractive tinting is a plus; unattractive staining is a minus (unless locality-defining, as in hourglass selenite).

• Aesthetics:

  • Overall composition—how the piece sits, the interplay of blades, and light transmission—matters as much as any single metric.
  • Backlighting can dramatically enhance clear selenite, but top pieces remain compelling under ambient light.

Detecting Repairs or Treatments

• Repairs:

  • Due to perfect cleavage, breaks are sometimes reattached. Look for straight, planar junctions, slight misalignments, or glossy glue seams along a cleavage plane.
  • A UV torch can reveal fluorescing adhesives in some cases. Always ask sellers to disclose repairs.

• Polishing and Enhancements:

  • Edges or faces may be lightly polished to conceal scratches or chips. Polished areas can look unnaturally smooth or mirrorlike compared to natural growth textures.
  • Desert roses can be reassembled or stabilized; inspect for atypical glue residues between blades.

• Fakes:

  • Fully synthetic selenite is rare in the specimen market; more common are assembled or overly polished pieces. Natural selenite shows subtle growth features, cleavage steps, and occasional internal veils or inclusions.

Care and Storage

Selenite is delicate. Proper care preserves clarity and crisp edges.

• Handling:

  • Always support from the base; avoid gripping thin edges or terminations. Consider cotton gloves to prevent fingerprints on glassy faces.
  • Keep selenite away from harder minerals that can scratch it; store each piece individually.

• Cleaning:

  • Best practice is dry cleaning: use a soft blower, gentle artist’s brush, or microfiber cloth.
  • If necessary, use the lightest possible damp wipe with distilled water and immediately dry. Never soak; prolonged contact with water can etch or dull surfaces and may loosen adhesives.
  • Avoid ultrasonic cleaners, steam, acids, or strong chemicals—these can damage selenite or its matrix.

• Environment:

  • Selenite is slightly soluble and sensitive to humidity; maintain a stable, dry environment. Avoid display near humidifiers or in bathrooms.
  • Keep away from heat sources and intense sunlight; elevated temperatures can dehydrate gypsum (toward bassanite/anhydrite) and may cause warping or micro-cracking.
  • Display lighting should be cool (LED) and not heat the specimen.

• Mounting and Transport:

  • Use soft mineral tack sparingly and on robust contact points; do not press on delicate edges or twin junctions.
  • For transport, wrap in soft tissue or foam with rigid boxing so nothing touches the edges. Mark “Fragile – Cleavage” on containers.

With mindful handling and a stable, dry display, selenite will retain its brilliant luster, transparency, and elegant forms for decades—an enduring, tranquil centerpiece in any mineral cabinet.