Overview

Witherite (BaCO3) is the barium carbonate species best known to collectors for its distinctive pseudo-hexagonal crystal twins and striking fluorescence. Though orthorhombic, it commonly forms penetration twins in triplets (and cyclic multiples) that mimic hexagonal prisms and “six-pointed stars.” Crystals are typically white to cream, sometimes grayish or pale honey, with a vitreous to slightly silky luster; stalactitic and botryoidal growths are also classic. The species is notably dense for a carbonate and often occurs with fluorite, galena, sphalerite, calcite, and baryte in low-temperature hydrothermal veins.

The most famous witherite specimens come from northern England’s Pennine orefield, especially the Settlingstones and Alston Moor mines, where sharp, sculptural twinned crystals on contrasting matrix defined the species for generations. Many English examples fluoresce bright white to blue-white under shortwave UV (some phosphoresce), making witherite an engaging display species both in ambient light and under UV lamps. Fine pieces are uncommon and increasingly difficult to source today, and well-formed twins with good luster, strong UV response, and attractive matrix command strong prices.

Popularity

Witherite is a connoisseur’s carbonate. It lacks the rainbow colors of showier species, yet its unusual twin morphology, historical English pedigree, and lively fluorescence keep it in steady demand. European museums and classic collections often include a textbook Settlingstones twin, while advanced collectors seek aesthetic matrix pieces from Alston Moor localities like Nentsberry Haggs, Tynebottom, Brownley Hill, and Dry Gill.

Availability is limited. Mining in the classic English vein systems ceased long ago, so most material trades on the secondary market. Attractive single crystals and small clusters remain attainable for newer collectors, but balanced matrix pieces with sharp, large twins are scarce and increasingly prized. With heightened interest in fluorescent displays, strongly reactive examples have seen a renewed uptick in popularity.

Top Collecting Localities

While witherite occurs worldwide, the northern England localities define the species for collectors. The following sites are especially renowned for quality, form, and historical importance.

Settlingstones Mine, England

Arguably the world’s most famous witherite locality, Settlingstones (Northumberland) produced iconic pseudo-hexagonal twins and cyclic multiples with excellent luster and translucency. Many show crisp faces and sharp terminations in stacked groupings, often perched on fluorite-bearing matrix. Under shortwave UV these crystals typically glow a brilliant bluish-white, sometimes with a lingering phosphorescence. The combination of form, size, and fluorescence set the standard; intact matrix specimens with few or no dings are the benchmark for the species.

Nentsberry Haggs Mine, Alston Moor, England

Nentsberry Haggs is renowned for stout, well-formed witherite twins with a slightly satiny luster, frequently set among sulfides and fluorite for strong contrast. Compared with Settlingstones, crystals here can look a touch more massive but remain highly aesthetic. Many pieces fluoresce powerfully under SW UV. Older classic specimens from 19th–20th century finds are now scarce; undamaged terminations and balanced arrangements elevate value significantly.

Fallowfield Mine, Hexham, England

An important historical source, Fallowfield produced handsome witherite twins and aggregates, sometimes with a warm cream tone and a satiny sheen. Fluorite and galena associations are common. While production was never as prolific as Settlingstones, choice pieces represent quintessential English witherite and are well regarded for their old-mine character and strong UV activity.

Collector’s Guide

Evaluating Specimen Quality

• Crystal Form and Twinning: The hallmark of witherite is its penetration and cyclic twinning that yields pseudo-hexagonal prisms and “six-pointed” clusters. Look for crisp, symmetric twins with sharp edges and well-defined terminations. Curved faces are common, but should still present clean, coherent forms. Multiple intergrown twins arranged aesthetically on matrix add appeal.

• Luster and Surface: Top specimens show a bright vitreous to subtly silky luster with fresh, glassy faces. Dull or chalky surfaces are less desirable unless the piece offers exceptional form or size. Avoid severe etching or granular surfaces that obscure the twinning.

• Color and Translucency: Most witherite is white to cream; lightly honeyed tones can be attractive. Subtle translucency, especially near edges and tips, enhances depth. Severe discoloration or pervasive stains reduce aesthetics unless historically important.

• Matrix and Associations: Contrasting matrix elevates display impact—purple fluorite, dark galena/sphalerite, or quartz can frame white twins beautifully. A well-balanced composition, with the main twin prominently positioned and free from crowding or awkward contacts, is ideal.

• Size and Completeness: Because damage at the tips is common, prioritize intact terminations on the main crystal(s). A smaller perfect twin generally outshines a larger one with obvious dings. Groups of multiple undamaged twins are especially prized.

• Fluorescence: Strong shortwave UV fluorescence (often bright bluish-white) is a celebrated feature. Pieces that glow intensely and evenly are popular for fluorescent displays; phosphorescence adds bonus appeal.

Detecting Repairs or Treatments

• Repairs: Older English specimens were sometimes reattached to matrix or rejoined at clean breaks. Inspect for straight glue lines, slight misalignments in striations, or a glossy seam along fractures. Some epoxies fluoresce under UV—use LW/SW to check for halos at joins. A single, well-executed repair may be acceptable on a significant piece, but multiple or sloppy fixes should lower value.

• Surface Enhancements: True polishing of witherite terminations is uncommon and generally discouraged. A perfectly mirror-flat tip with unnatural gloss could indicate polishing. Cleanliness is usually achieved through gentle washing, not chemical alteration.

• Fakes: Lab-grown witherite is not a concern in the specimen market. Imitations are rare; natural twinning, subtle curvature, and internal textures are hard to counterfeit.

Care and Storage

Witherite is a relatively soft and brittle carbonate (Mohs ~3–3.5) and contains toxic barium in soluble form; take sensible precautions.

• Handling and Safety:

  • Avoid touching crystal tips; support matrix pieces with both hands.
  • Do not lick or mouth specimens; wash hands after handling.
  • Keep away from children and pets. Consider a display case for safety.

• Cleaning:

  • Dust gently with a soft brush or air bulb.
  • If needed, use lukewarm water with a drop of mild dish soap; rinse and dry promptly.
  • Avoid acids and harsh cleaners—acids can attack carbonates and may drive alteration to baryte.
  • Do not use ultrasonic or steam cleaners; vibrations/heat can induce cracking.

• Environment:

  • Store in stable, moderate conditions away from direct sunlight and heat sources.
  • Normal indoor humidity is fine; avoid prolonged dampness or repeated wet/dry cycling which can encourage alteration films.
  • Most witherite is reasonably light-stable, but long-term intense sunlight is never recommended for minerals.

• Mounting and Transport:

  • Use inert, non-acidic supports. Avoid acidic foams or papers.
  • Secure specimens with minimal, reversible mineral tack when displayed; cushion well during transport to protect tips.

• UV Display:

  • Shortwave UV can be used regularly for viewing; the fluorescence is a highlight of the species.
  • As with any UV use, shield eyes/skin appropriately and avoid excessive heating of enclosed cases.

By focusing on sharp twinned form, bright luster, clean terminations, strong UV response, and attractive matrix contrast, collectors can assemble a refined suite of witherite that illustrates both the beauty and the mineralogical uniqueness of this classic English carbonate.