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Gahnospinel Gemstone: Properties, Meanings, Value & More

半尖晶石寶石：屬性、意義、價值等

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Gahnospinel is an often blue, zinc-rich variety of spinel with impressive durability. Technically, it falls between two minerals in the spinel group: spinel and gahnite, hence the name.

What is the rarest spinel? Blue spinels are rare, but gem-quality gahnospinels are even rarer than natural blue spinels. Red and cobalt-blue are the most expensive spinel colors.

Ready to know more about this rare, beautiful spinel variety? Our Coins Auctioned experts have rounded up all the properties, history, prices, and benefits of gahnospinel in today’s guide.

Pictured above: Faceted "cobalt blue" gahnospinel weighing 1.01 carats studied by Gemological Institute of America (GIA)| Image credit: Lhapsin Nillapat via GIA

What Is Gahnospinel?

Gahnospinel is a gemstone in the spinel family between gahnite and spinel. The gem is usually pale to dark blue but can be other shades of blue, including greenish-blue and violet.

Other monikers for this semi-precious gemstone include zincian spinel and aluminous magnesium-zinc spinel.

As a spinel variety, gahnospinel is an August and Leo birthstone. It can even substitute for sapphire as a September birthstone.

Gahnospinel Specifications & Characteristics

Gahnospinel’s composition is between gahnite (ZnAl2O4) and spinel (MgAl2O4), two minerals in the spinel group that form a solid solution series.

In gahnospinel, zinc substitutes for magnesium to varying degrees, making gahnospinel’s formula (ZnMg)Al2O4 or (MgZn)Al2O4.

The zinc content changes certain properties in the mineral; the refractive index (RI) and density of gahnospinel is higher than spinel but lower than gahnite. The Mohs hardness of gahnospinel similarly sits at 7.5 to 8, though.

A small amount of iron oxide is usually present, ranging from around 1.5 to 2.5 percent in Sri Lankan gahnospinels.

Identifying gahnospinel can be tricky, as it looks similar to regular spinel and has similar RI values to synthetic spinel. Testing requires advanced equipment and skill to identify any zinc present.

Gahnospinel properties listed:

• Mohs hardness: 7.5-8

• Color: Shades of blue, greenish-blue, green, bluish-violet, violet

• Crystal structure: Isometric/Cubic

• Luster: Vitreous

• Transparency: Transparent to near-opaque

• Refractive index: 1.72-1.78; Increases with higher zinc content

• Density: 3.60-4.10; Increases with higher zinc content

• Cleavage: None; Indistinct parting on {111} separation plane

• Fracture: Conchoidal

• Streak: White

• Luminescence: None

• Pleochroism: Usually none, sometimes present anomalously

• Birefringence: None, sometimes present anomalously

• Dispersion: 0.020 (moderate)

Pictured above: Sharp, lustrous, bluish-black octahedral gahnite crystal | Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Gahnospinel History

We have three British gemologists to thank for the naming and discovery of gahnospinel: Basil William Anderson, Cecil J. Payne, and T.W. Oliver.

Studying blue spinels from Ceylon (present-day Sri Lanka), Anderson and Payne noticed that some had unusually high refractive indices (RI) and densities. In 1935, Oliver showed them a similar blue spinel that didn’t seem to be iron-rich.

Anderson and Payne looked through parcels of blue Sri Lankan spinels and discovered that 1) around 1% were “high” spinels, and 2) all contained zinc.

They guessed the property-raising element was zinc, and Dr. Max Hey conducted an analysis that proved them right: their “top” specimen contained 18-21% zinc oxide and 16-78% magnesium oxide.

Since the properties fell between gahnite and spinel, Payne and Anderson named the mineral “gahnospinel” in their first description of gahnospinel in 1937. (The name “gahnite” was chosen in 1807 to honor Swedish chemist Johan Gottlieb Gahn.)

In 1964, Anderson and Payne achieved their second goal of finding a gahnospinel specimen with an RI over 1.750 and a density over 4.00.

Pictured above: Faceted "cobalt blue" spinel gemstone

Gahnospinel Healing Properties

As a blue healing stone, gahnospinel possesses the soothing and balancing properties of other blue gemstones.

Physical Healing

Physically, gahnospinel gemstone benefits are said to include treating issues like:

• Blood detoxification

• Gum / tooth diseases

• Throat pain

• Vision problems

• Memory loss

• Low stamina

Emotional Healing

Emotionally, crystal healers recommend gahnospinel for:

• Promoting honesty

• Raising intuition

• Boosting motivation

• Providing protection

• Fostering relationship harmony

• Encouraging creative expression

• Revitalizing your spirit

Chakra Healing

Chakra healing involves opening an energy center (chakra) that’s blocked so energy can flow freely throughout the entire system again.

Gahnospinel is a chakra stone for the throat and third eye chakras, located at the throat (of course) and center of your forehead, respectively.

The throat chakra governs communication and self-awareness, while the third eye chakra governs intuition and perception.

When both are opened, you can gain a greater understanding of both yourself and the world around you.

Pictured above: The largest faceted gahnospinel (11.34 carats) identified by the Gemological Institute of America (GIA) | Image credit: Diego Sanchez via GIA

Gahnospinel Gemstone Properties

Besides rarity, other factors affecting gahnospinel’s value include color, cut, clarity, and carat weight.

Color

Typically, gahnospinel’s color comes from traces of iron, creating muted dark blues. Gahnospinels with more zinc may be more greenish-blue, but pure blue is best.

Recently, researchers have discovered blue gahnospinels colored by cobalt, published by the Gemological Institute of America (GIA) in 2022 and Gemmology Today in 2019. These rare cobalt-blue gahnospinels are most valuable.

Cut

Given the rarity of facetable material, faceted gahnospinels are generally priciest. Most have round, oval, or cushion shapes.

Otherwise, gahnospinel for sale is often available as small, uncut crystals.

Clarity

Spinel has Type II clarity, so some visible inclusions are common. No visible inclusions (“eye-clean”) mean higher prices.

Common inclusions in gahnospinel include:

• Small particle stringers (fingerprints or straight lines)

• Octahedra (cavities or crystals), sometimes surrounded by liquid feathers

• Apatite

• Intersecting needles

• Iridescent thin films

Green gahnospinel inclusions in metamorphic sapphires often indicate that the sapphires came from Sri Lanka.

Carat Weight & Size

Most faceted gahnospinels are under 2 carats, with rare exceptions like an 11.34-carat faceted gahnospinel examined by GIA in 2019.

Gahnospinel price-per-carat increases over 1, 2, and 5 carats.

Gahnospinel Formation & Sources

Gahnospinel can form in metamorphic or igneous rocks. Metamorphic formation generally results in more magnesium, while igneous results in less magnesium.

Usually, gahnospinel forms through metamorphic means. It’s found in gem gravels washed down from alluvial deposits that formed when the host rock eroded.

Mining Locations

Most gem-quality gahnospinel comes from Sri Lanka.

The only other significant sources are the Czech Republic and Nigeria.

Pictured above: Relative of gahnospinel, a faceted 1.34-carat gahnite gemstone from Argentina | Image credit: Kay Günther / G-Empire The World of Gems / http://www.g-empire.de/

Gahnospinel Price & Value

Faceted gahnospinel gemstone value ranges from around $60-$1,070 per carat, or about $200-$4,650 total, with pricier ones being larger and brighter colored.

Matched faceted pairs are on the high end, usually around $640 per carat or $275 total.

Rough, transparent gahnospinel crystals range from about $40-$120 per carat, or $100-$250 total.

Gahnospinel Care and Maintenance

Luckily, gahnospinel has good wearability, making gemstone care easy. You can sport all any jewelry, including gahnospinel rings, without concern.

Clean gahnospinel with warm water, mild soap, and a soft toothbrush.

Ready to Glow with Gahnospinel Gems?

Gahnospinel is an underrated member of the spinel family. It pairs gorgeous blue hues with soothing benefits, all in a durable form perfect for any jewelry or display.

Buy gahnospinel and other stunning gemstones today!