Sellaite Gemstone: Properties, Meanings, Value & More

Sellaite is a colorless to white magnesium fluoride mineral first discovered in France in the 1800s. The sellaite mineral isn’t well-known to anyone beyond collectors, partly for its extreme rarity.

Not only are sellaite crystals small, but cuttable material has only come from one source and not in large amounts. Only a small number of low-carat sellaite gemstones have been cut.

Want to learn more about this obscure stone? Come along as we break down sellaite’s properties, history, prices, and more!

Pictured above: Gemmy sellaite crystal from Carlos Barbosa's personal collection | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

About Sellaite Stone

Sellaite is an extremely rare, colorless to white semi-precious gemstone. Other monikers for the stone are:

• Belonesite

• Belonosite

By their names and common colors, you may mix up sellaite with selenite. However, selenite is a variety of gypsum (composed of hydrous calcium sulfate) while sellaite is composed of magnesium fluoride.

Additionally, selenite is significantly lower on the Mohs hardness scale (at 2 or 3) than sellaite and selenite has a lower density (2.25 to 2.35). Not only that, selenite is a lot more common than sellaite.

Sellaite Uses

Given sellaite’s rarity, scientists have created synthetic sellaite alternatives for industrial uses.

One recently patented process invented by Viktor Ivanovich Petrik and Vladimir Petrovich Lyashenko was published in 1997.

Petrik and Lyashenko’s process involves using an aqueous suspension of magnesium carbonate to precipitate magnesium fluoride with hydrofluoric acid. They then introduce an aqueous solution of ammonium fluoride to separate the precipitated magnesium fluoride, which is dried into a powder. The powder is then treated with heat and pressure in a vacuum.

This synthetic sellaite was created to potentially use as an optical material for making semi-finished optical ceramic products like lenses and windows.

Synthetic sellaite can also be used for polarizing prisms and ceramics. A major benefit of synthetic sellaite in optics applications is that transparent magnesium fluoride stays transparent over a very broad range of wavelengths.

Additionally, magnesium fluoride is useful as an anti-reflective coating on glass. This is helpful for applications like Interference Reflection microscopy (reflection interference contrast microscopy), a technique for studying cell mobility and adhesion with a microscope.

Pictured above: Chinese (Mainland China): Magnesium fluoride, chemically pure (CP), content 98.0%~101.0% (translated from Chinese) | Image credit: Leiem, CC-BY-SA-4.0

Sellaite Specifications & Characteristics

As a magnesium fluoride mineral, sellaite’s formula is MgF2. The stone is in the halide group of minerals, which have a dominant halide anion like fluoride, chloride, bromide, or iodide — in this case, the halide anion is fluoride. Another halide you may know is the sodium chloride mineral halite.

Structurally, sellaite is related to the rutile mineral group, which are tetragonal oxides like argutite, cassiterite, pyrolusite, and of course, rutile.

In terms of crystal habits, sellaite can form stout, prismatic, flattened, pyramidal, or acicular individual crystals. It can also occur as fibrous, radial, or spherulitic aggregates. Twinning can happen on {011}. Usually, sellaite occurs as glassy prisms.

Sellaite properties listed:

• Mohs hardness: 5-5.5

• Color: Colorless, white, very pale yellow

• Crystal structure: Tetragonal

• Luster: Vitreous (glassy)

• Transparency: Translucent to transparent

• Refractive index: 1.378-1.390

• Density: 3.15

• Cleavage: Perfect on {010} and {110}; Crystals may be too small for cleavage to be observed

• Fracture: Conchoidal

• Streak: White

• Luminescence: Usually none; Sometimes blue in LW-UV; Pale violet luminescence on cleavage when warmed

• Pleochroism: None

• Birefringence: 0.012 (very weak)

• Dispersion: Unknown

Enough mineralogy for now, it’s time to step into sellaite’s past.

Pictured above: Portrait of Quintino Sella, sellaite's namesake, circa 1870 | Image credit: Annales.org, Public domain

Sellaite History

Italian paleontologist and mineralogist Johannes (or Giovanni) Strüver published the first description of sellaite in 1869 based on specimens discovered in the Gébroulaz glacier, located in the Auvergne-Rhône-Alpes of France.

Strüver chose the name “sellaite” to honor Italian politician, mineralogist, and professor Quintino Sella.

In 1886, Italian physician, mineralogist, and naturalist Arcangelo Scacchi published a description of sellaite found in Vesuvian lava in 1872. However, Scacchi called the mineral “belonesia” or “belonesite,” and believed it was magnesium molybdate.

Scacchi’s mineral was later proven to be the magnesium fluoride sellaite by Italian mineralogist Ferruccio Zambonini in 1899.

Methods of Sellaite Synthesis

The foundation of sellaite synthesis was in 1811, when French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard dissolved magnesium oxide in hydrofluoric acid.

The first synthetic production of magnesium fluoride occurred in 1824, when Swedish chemist Jöns Jacob Berzelius created it with two (separate) methods: by treating magnesium carbonate with hydrofluoric acid and by using a magnesium sulfate solution and potassium fluoride to precipitate the mineral.

Other processes after that of Berzelius include:

• 1862 – By F. Röder; Process: Melting 5 parts magnesium chloride with 4 parts sodium fluoride and 4 parts sodium chloride, then cooling

• 1887 – By French chemist Henri Moissan; Process: Burning the powdered metal in fluorine gas, creating a combustion avec beaucoup d'eclat (“with a lot of sparkle”)

• 1887 – By A. Feldmann; Process: Heating magnesium chloride with calcium fluoride, digesting the product with water acidified with hydrochloric acid to create magnesium fluoride powder; Can be crystallized (according to Italian chemist Alfonso Cossa) by cooling the fused fluoride or melting it with alkali chlorides

Back to the metaphysical, let’s look at sellaite’s spiritual benefits.

Image credit: National Gem Lab

Sellaite Healing Properties

As a colorless healing stone, sellaite has the cleansing and protective properties of other white gemstones.

Physical Healing

Physically, sellaite is said to help with issues related to:

• Nervous system

• Pituitary gland

• Cognition

Emotional Healing

Sellaite is believed to facilitate self-realization and spiritual connection. As a colorless stone, sellaite may boost mental clarity, stabilize emotions, and cleanse the soul of negativity.

Chakra Healing

Chakra healing involves identifying the energy center (chakra) associated with any current negative symptoms you’re experiencing. These symptoms are thought to be the result of that chakra’s energy flow being blocked or unbalanced.

Sellaite is used as a crown chakra stone. The crown chakra is the highest chakra, located atop your head as a swirling halo that beams upwards. This energy center governs enlightenment, connection to the divine, and abstract thinking.

Symptoms of a blocked crown chakra include feeling disconnected and confused, along with a strong need for control.

After using sellaite, you’ll know the crown chakra is opened when you feel connected to yourself, elevated, and at-one with the universe.

Sellaite Gemstone Properties

Since sellaite gemstones are so rare, there aren’t standard grading procedures. That said, we’ll still go over how the general value factors may apply to sellaite:

• Color: Sellaite can be colorless, white, or slightly yellowish, though they’ll display a pale violet luminescence when cleaved and warmed up. More pure, even coloring can be more valuable.

• Cut: The extreme rarity of facetable sellaite material makes faceted sellaites extremely valuable. The stone is usually sold rough (uncut).

• Transparency: Since many crystals are only fully transparent in small areas, greater transparency can be more valuable. Many crystals are also too small to appear fully transparent.

• Carat Weight & Size: The largest sellaite crystals currently known are about 5 cm (almost 2 in) long, and only Brazil has produced cuttable sellaite. As such, only a few gems weighing about 2 carats max (usually less) have been faceted.

Back to the mineral’s foundation, how does sellaite form?

Pictured above: Small balls of ferroaluminoceladonite in assemblage with beryl, sellaite, pyrite, and topaz | Image credit: Ralph Bottrill, CC-BY-SA-3.0

Sellaite Formation & Sources

Sellaite is found in a broad range of geological environments, forming from gasses, fluids, and melts under different pressure and temperature conditions.

The mineral can be found in:

• Evaporites

• Metamorphic magnesite

• Soda-granite

• Pegmatites

• Volcanic ejecta & fumaroles

• Marble

• Dolostone

The only known facetable material has come from metamorphic magnesite deposits.

Common associated minerals are:

• Anhydrite

• Gypsum

• Sulfur

• Fluorite

• Celestite

• Magnesite

• Quartz

That covers the geological side, but where does sellaite come from geographically?

Mining Locations

Currently, the only known source of facetable sellaite material is Bahia, Brazil.

The only other verified sources of the mineral are:

• Colorado, USA

• France

• Germany

• Italy

• Norway

• Peru

• Russia

Now, how much do sellaite gemstones and specimens cost?

Pictured above: Sellaite crystal displayed at the Smithsonian Museum of Natural History | Image credit: Bram Hasler, Fine Mineral Blog

Sellaite Price & Value

Perhaps unsurprisingly, faceted sellaite gemstones command the highest prices.

Of the rare few out there, colorless faceted sellaites are usually around $500 per carat. Remember: The total price may be slightly lower if the weight is under 1 carat.

More yellow or translucent faceted sellaites (of lower quality) can be around $20 to $30 per carat.

Rough sellaite is significantly lower in price, starting around $15 and reaching about $55 each.

Sellaite Care and Maintenance

Before we cover gemstone care, it’s important to note that magnesium fluoride can be toxic if ingested or inhaled. This mainly poses a risk for lapidarists who cut the gem, who should use proper safety equipment.

For display purposes, keep sellaite away from anyone who might put it in their mouth, like children or pets.

In terms of caring for sellaite, the crystal is slightly soluble in water and will decompose in concentrated sulfuric acid.

As such, only clean sellaite by wiping it down with a dry, microfiber cloth and store it in a dry, cool place.

Are You Sold on Sellaite?

Sellaite is a rare mineral and even rarer gemstone, but its rarity only adds to its value and appeal, especially for collectors. Given the various synthetic processes created, we may just see synthetic sellaite gemstones available in the future.

Buy sellaite and more gemstones today!