THE WAND & THE CRYSTAL BALL SOCIETY · PECKHAM

Stibnite: What It Is, Why It Costs What It Costs, and How to Keep It

What it is and how the crystals form

Stibnite (antimony sulphide, Sb₂S₃) is a metallic‑grey sulphide that commonly occurs as long, slender prisms with a distinctive silky luster. It forms in low‑temperature hydrothermal veins where antimony‑rich fluids precipitate the mineral as the temperature drops. Typical environments include the oxidised zones of lead‑zinc deposits and the peripheral parts of volcanic fumaroles. In the United Kingdom the most celebrated occurrences are the St. Just mines in Cornwall and the historic lead workings of Derbyshire, where stibnite crystals grow alongside galena and sphalerite.

How to judge a good specimen

A quality stibnite piece is judged by several visual and tactile criteria:

• Crystal habit: Well‑formed, elongated prisms that are straight or gently curved, often with a slight taper towards the tip.
• Surface texture: A smooth, glassy to silky sheen is preferred; heavy surface pitting or excessive weathering reduces value.
• Colour consistency: Uniform metallic‑grey to steel‑blue tones are typical; bright yellowing or brown staining usually indicates oxidation.
• Size and grouping: Larger individual crystals are prized, but a tight cluster of well‑aligned prisms can be equally attractive.
• Stability: Stibnite is relatively soft (Mohs 2 – 2.5) and brittle; a specimen that shows no obvious fractures or powdery loss is a good sign.

What affects the price

Price is a function of market demand, provenance and the physical attributes listed above. Specimens from classic localities such as Cornwall or Derbyshire command a premium because of their historical significance and collector familiarity. Size matters – a single crystal exceeding a few centimetres in length will fetch more than a comparable mass of smaller fragments. Crystal quality, particularly the presence of well‑developed terminations and a lack of surface alteration, also drives price. Finally, the overall presentation – a clean, well‑mounted piece with a clear label – adds commercial value.

How to tell it from lookalikes

Stibnite can be confused with a few other metallic sulphides. The following points help to separate it from common impostors:

• Pyrite (FeS₂): Pyrite is cubic or octahedral and displays a brassy yellow colour, whereas stibnite is elongated and grey‑blue.
• Marcasite (FeS₂ polymorph): Like pyrite it forms tabular crystals and lacks the silky luster of stibnite.
• Realgar (As₄S₄): Realgar is orange‑red and brittle, never presenting the metallic grey hue of stibnite.
• Orpiment (As₂S₃): Bright yellow and flaky, it is easily distinguished by colour.
• Galena (PbS): Galena forms cubic crystals with a lead‑grey colour and a higher specific gravity; a simple hardness test (stibnite scratches easily) will separate the two.

Care and safety

Stibnite is soft and can be damaged by handling, so it should be stored in a padded container, preferably wrapped in acid‑free tissue. Avoid direct contact with acids or strong bases, as the mineral can release antimony compounds that are toxic if inhaled or ingested. When cleaning, use a soft brush or a gentle air‑blow; never apply water or solvents. Because antimony is a recognised occupational hazard, wear gloves when handling large quantities or when cutting specimens, and work in a well‑ventilated area.

In a market where mystery boxes are common, a photographed, priced piece offers certainty. You can assess crystal habit, colour and provenance before purchase, ensuring that the specimen meets your expectations and that the price reflects its true quality. This transparency eliminates the risk of receiving a damaged or misidentified mineral, making a documented sale the smarter choice for any serious collector.

Peckham Crystals · The Wand & The Crystal Ball Society, Rye Lane Market, Peckham, London SE15 5BY ·
info@increatus.com · 07961 945999. Prices are UK retail estimates, not guarantees.