Senarmontite Gemstone: Properties, Meanings, Value & More

Senarmontite is an antimony oxide mineral primarily found as small crystals with gray hues. Mineral collectors seek out senarmontite in translucent, pale gray, octahedral crystals.

In terms of rarity, senarmontite is fairly uncommon as a mineral, though it has been found in over a dozen countries. As a gemstone? It’s incredibly rare. Not only is it too soft to wear in jewelry, but it’s also scarcely found as gem-quality material.

Another key aspect of senarmontite gemstones is their toxicity, which is why knowing how to handle them safely is key. We’ve learned a thing or two after spending decades handling gemstones, so we’ve gathered up everything you need to know about the properties, uses, history, safety guidelines, and prices of senarmontite stones.

Pictured above: Clean, clear, and sharp colorless senarmontite octahedral crystal from Algeria; Charlie Key Collection | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

About Senarmontite Stone

Senarmontite, formerly spelled sénarmontite, is a colorless to gray mineral very rarely used as a semi-precious gemstone.

As a commonly gray gemstone, senarmontite is beneficial to those born under Capricorn between December 22 and January 19.

Much of the intrigue surrounding senarmontite, though, comes from its industrial uses. So, what is senarmontite used for?

Senarmontite Uses

Senarmontite contains antimony, an element that’s lesser-known by the masses but immensely important to a whole host of industries. The primary mineral source of antimony is stibnite, an antimony sulfide mineral, but senarmontite is the only antimony trioxide mineral besides valentinite.

Some of the most important uses of antimony sourced from senarmontite include:

• Catalyst (e.g. for producing plastic bottles & fluorescent light bulbs)

• Lead & Tin Alloy Hardener (e.g. lead-acid rechargeable batteries, bullets, machine slide bearings, solders)

• Semiconductor Dopant (e.g. silicon wafers, infrared detectors, diodes)

• Potential Anode for Lithium-Ion Batteries

• Solar Panel Glass Stabilizer

• Pigments (like historic “Naples Yellow” or modern white pigment & opacifier used in glass, paints, ceramics, and enamels)

Antimony trioxide specifically is used in halogenated flame retardants, which covered 48% of the antimony uses worldwide in 2017.

Pictured above: Small cluster of senarmontite crystals, 26 x 22 x 21 mm. K. Nash specimen and photo. | Image credit: Kelly Nash, CC-BY-SA-3.0

Senarmontite Specifications & Characteristics

Senarmontite is an antimony trioxide mineral with the formula Sb2O3. The mineral valentinite has the same composition but it crystallizes with orthorhombic symmetry while senarmontite has isometric (cubic) symmetry.

The arsenic oxide arsenolite is also isostructural with senarmontite, meaning they have the same structure but different compositions.

Senarmontite crystals are usually octahedral, sometimes modified by dodecahedron and cube crystals. They can be found individually or in crystal clusters. The mineral also occurs as crusts or granular masses.

Although senarmontite is isotropic, it has significant anomalous anisotropism that may be zoned or sectored.

Senarmontite properties listed:

• Mohs hardness: 2-2.5

• Color: Colorless, grayish-white, gray

• Crystal structure: Isometric/Cubic

• Luster: Resinous, pearly, or sub-adamantine

• Transparency: Translucent to near-opaque; Rarely transparent

• Refractive index: 2.087

• Density: 5.50

• Cleavage: Poor/Indistinct in traces (interrupted) on {111}

• Fracture: Irregular/uneven

• Streak: White

• Luminescence: None

• Pleochroism: None

• Birefringence: None

• Dispersion: None

Pictured above: Ultrapure metallic antimony piece | Image credit: Jurri, CC-BY-SA-3.0

Senarmontite History

Antimony goes back to ancient times. It was used in ancient Egyptian kohl makeup as early as 3100 BC, along with 3000-BC Chaldean ornaments, 1st-century AD Roman medicines, and 14th-century AD European alchemist projects.

Senarmontite, on the other hand, has a slightly more recent history.

French mineralogist and physicist Henri Hureau de Sénarmont first described senarmontite in 1851. Sénarmont based his report on octahedral cavernous masses made up of capillary (thread-like) filaments.

These specimens came from the Djebel Hammimat Mine in Constantine, Algeria. This mine, now senarmontite’s type locality, had only been discovered a few years earlier in 1845. It was also Algeria’s first antimony deposit ever worked.

In his description published in the Annales de Chimie et de Physique (French for Annals of Chemistry and Physics), Sénarmont described the mineral as an oxide of antimony.

The mineral’s name came later that year (1851) when American geologist and mineralogist James Dwight Dana published a lengthier description of the “Octahedral oxyd of Antimony” in the American Journal of Science and Arts. Dana noted other habits — compact or granular saccharoid (sugar-like) masses — of the mineral from another mine.

At the end of his description, Dana wrote “Senarmontite is an appropriate name for this octahedral oxyd,” honoring the stone’s discovery by Sénarmont.

Besides the terms “antimony oxide” or “cubic antimony trioxide,” mineralogists also used the spelling “sénarmontite” alongside “senarmontite.” In 2015, the International Mineralogical Association (IMA) officially chose the spelling “senarmontite” without the acute accent e.

Pictured above: Small miniature of sharp octahedral senarmontite crystals found from the type locality | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Senarmontite Healing Properties

As a commonly gray healing stone, senarmontite has the calming and balancing properties of other grey gemstones. It can also be used in energy healing as a root chakra stone.

Physical Healing

Using senarmontite for healing physical ailments goes back to ancient times. In 77 AD, Roman scholar Pliny the Elder wrote about antimony compounds being used for:

• Cooling

• Making tissues contract (astringent)

• Treating eye problems

• Stopping blood discharge from the brain

• Soothing burns and wounds

Given the toxicity of antimony, we do NOT recommend using senarmontite in its physical form for treatment (e.g. applying it as a powder to your body), only spiritually.

Emotional Healing

On the emotional end, senarmontite is said to alleviate stress, increase focus, enhance willpower, and protect you from negative energies both external and internal.

Senarmontite Gemstone Properties

Given its rarity in gem-quality form, senarmontite doesn’t have any standard grading criteria. But we’ll still go over how the traditional factors can apply to senarmontite value:

• Color: Senarmontite crystals closer to colorless or pale gray are generally higher value than dark gray or murky crystals.

• Cut: Senarmontite gemstones often have a faceted cut that preserves the most gem-quality rough, like square or step cuts.

• Transparency: Most senarmontites are too dark to have good transparency, so any degree of translucence will increase value, even if inclusions are visible.

• Carat Weight: You might come across some faceted senarmontites up to 1-2 carats. A couple of faceted senarmontites have been larger than you’d expect — between 4 to 6 carats — but they’re too soft to wear and usually reserved for museums or auctions. Most well-formed senarmontite crystals are fairly small, but crusts or masses can be much larger.

Before it even reaches the market, how does senarmontite form in the first place?

Pictured above: Large plate of sharp senarmontite crystals from type locality in Algeria | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

A large plate of sharp crystals to 4mm, from this type locality for the species. I believe they were found during expeditionary work by French geologists, and much of this was brought back and put into French museums and dealerships at the time. Large specimens are very rare - usually i see only thumbnail loose crystals on the market.

Senarmontite Formation & Sources

Senarmontite minerals are secondary minerals, meaning they form when primary minerals are altered in some way. In this case, antimony minerals like stibnite are oxidized and altered into senarmontite.

As such, senarmontite is usually found in hydrothermal deposits inside sedimentary rocks that contain stibnite.

Other minerals commonly associated with senarmontite are:

• Valentinite

• Kermesite

• Stibioconite

• Cetineite

• Mopungite

• Sulfur

• Barite

• Quartz

• Celestine

Mining Locations

The only known source of some facetable senarmontite crystals is the Djebel Hammimat Mine in Algeria — the mineral’s type locality.

Other important sources for attractive senarmontite crystals and specimens include:

• Canada

• England

• France

• Germany

• Italy

• Sardinia

• Slovakia

• USA (California, Nevada, South Dakota)

• Zimbabwe

Now, how much is senarmontite worth as a gemstone?

Senarmontite Price & Value

Senarmontite isn’t a mineral you’ll encounter often, but it’s also fairly low-demand so it doesn’t have the rarity price boosts of other stones.

The rare faceted senarmontite gemstones usually go for around $150 per carat.

Most senarmontite for sale is available as rough crystals or crystal masses. These specimens range based on their transparency, color, size, and form.

You can find small, well-formed senarmontite crystals that are translucent and pale to colorless for $25 to $60. Larger crystal clusters can be $100 to $250, with historical crystal specimens reaching near $1,000.

Pictured above: Rich senarmontite specimen from Algeria with waxy luster and gray octahedral crystals on massive senarmontite matrix | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Senarmontite Care and Safety

First and foremost, safe handling procedures are crucial for senarmontite. The antimony in the mineral is toxic and potentially carcinogenic when it's inhaled, and inhalable fibers scratch off easily given senarmontite’s very low hardness.

Our tips for handling senarmontite safely are:

1. Use proper gloves when handling the stone and still wash your hands thoroughly after handling.

2. Keep senarmontite away from anyone who might handle it unsafely, like pets or kids.

3. Store senarmontite in an enclosed, sealed container kept in a dry, cool area.

When it comes to caring for senarmontite, keep it away from moisture — it can dissolve in water. You can carefully clean by wiping it with a soft, microfiber cloth, being careful not to scratch off fibers that you could inhale.

Frequently Asked Questions

What is senarmontite?

Senarmontite is a rare, typically gray antimony trioxide mineral sought after by collectors in sharp, octahedral crystal habits with a pale pearly gray coloring. It’s better known industrially as a minor source of antimony.

Is senarmontite a gemstone?

It has been found as gem-quality crystals and is occasionally faceted, but senarmontite gemstones are quite rare.

Is senarmontite rare?

Senarmontite is relatively uncommon as a mineral but it’s very rare as a gemstone.

What is senarmontite used for?

Senarmontite is a minor antimony ore. Antimony trioxide compounds like senarmontite are primarily used for flame retardant compounds and alloys made with lead or tin like those used in rechargeable batteries.

What does the US use antimony for?

The United States uses antimony for products mentioned above like flame-retardant compounds and batteries, but a major sector for antimony use in America is the military. The production of various types of military supplies — e.g. sensors, night vision goggles, flares, bullets, tanks, and more — requires antimony. In the past couple decades, the US has worked on increasing domestic antimony sourcing, with Perpetua Resources reopening the historic Stibnite mine in Idaho.

Expand Your Rare Stone Collection with Senarmontite!

Senarmontite is a lesser-known mineral with a fascinating history and ever-increasing value industrially. With the proper safety protocol, you can add a gorgeous colorless or steely gray senarmontite crystal cluster to your rare mineral lineup!

Buy senarmontite and other rare gemstones today!