Kornerupine Gemstone: Properties, Meanings, Value & More

Kornerupine is a very rare gemstone beloved by collectors when it displays emerald-green hues, distinct pleochroism, or optical effects like asterism or chatoyancy.

How rare is kornerupine? The mineral is rare, and faceted gemstones are rarer, especially in larger sizes. Certain varieties like star kornerupine are extremely rare.

Though mostly known by gem collectors, kornerupine’s popularity has increased since new gem deposits were uncovered in Africa.

In this guide, we’ll highlight all of kornerupine’s properties, along with its prices, sources, varieties, and more.

What Is A Kornerupine Stone?

Kornerupine is a semi-precious gemstone, though its rarity exceeds that of some precious gemstones.

The stone is sometimes called “kornerupite” or “prismatine,” but prismatine was established as a separate mineral (though closely related to kornerupine) in 1996.

When kornerupine displays brighter green colors, it can substitute for emerald as a May birthstone and 20th wedding anniversary gem.

Kornerupine Specifications & Characteristics

Kornerupine is a borosilicate with the formula Mg3Al6(Si,Al,B)5O21(OH).

Common impurities are titanium, manganese, calcium, lithium, sodium, and fluorine. Chromium and vanadium are rare impurities that produce a valuable emerald-green hue.

The mineral forms a series with prismatine, which has a much longer formula of (◻,Fe,Mg)(Mg,Al,Fe)5Al4Si2(Si,Al)2(B,Si,Al)(O,OH,F)22. The two differ in iron, magnesium, fluorine, aluminum, and particularly boron content in one of the tetrahedral sites. If that boron content is under 0.5 atoms per formula unit (apfu), it’s kornerupine; over 0.5 apfu means it’s prismatine.

Kornerupine crystals may be slender and prismatic or radiating. It can also occur as fibrous masses. The stone’s optic character is biaxial (-), but some gems are pseudo-uniaxial.

Kornerupine properties listed:

• Mohs hardness: 6-7

• Color: Colorless, white, gray, black, brown, blue, various green shades, pink, yellow

• Crystal structure: Orthorhombic

• Luster: Vitreous

• Transparency: Transparent to opaque

• Refractive index: 1.661-1.699; Varies by locality

• Density: 3.27-3.45; Varies by locality

• Cleavage: Distinct/good on {110}

• Fracture: Conchoidal or uneven/irregular

• Streak: White

• Luminescence: Fluorescence sometimes present - Yellowish in LW-UV & SW-UV (green gems from Myanmar and East Africa)

• Pleochroism: Trichroism present, weak to strong; Usually colorless or green to colorless, pale brownish-yellow or pale-yellow-green to pale brownish-green or green or light amber; Additional colors vary by source (discussed further in Gemstone Properties)

• Birefringence: 0.013-0.017; Varies by locality

• Dispersion: 0.018 (moderate)

• Optical phenomena: Chatoyancy, asterism (very rare)

Pictured above: Cat's eye kornerupine

Types of Kornerupine

What are the different types of kornerupine? Kornerupine has two varieties characterized by optical effects:

1. Cat’s Eye Kornerupine: Displays a ray of light down the center — chatoyancy (the “cat’s eye” effect) — because of oriented rutile and graphite inclusions

2. Star Kornerupine: Displays 4 rays of light down the center resembling a star — asterism — because of criss-crossed inclusions

Both are rare, but star kornerupines are extremely rare.

Kornerupine Meaning & History

Kornerupine is sometimes called a “Stone of Personality and Character Transformation.” It represents stability, problem-solving, and new perspectives.

Danish mineralogist Johannes Theodor Lorenzen published kornerupine’s first description in 1884. The first material came from Greenland.

Lorenzen noted the material strongly resembled the sillimanite variety fibrolite. Once he confirmed it was a new mineral, he named it after Danish geologist and explorer Andreas Nikolaus Kornerup.

Kornerup made acclaimed expeditions to Greenland from 1876 to 1879, but tragically developed tuberculosis on the last trip, dying in 1881.

Star kornerupine was also discovered in 1884 but in Myanmar. The first Sri Lankan kornerupines (now the most abundant source) were discovered in 1954.

Another important discovery was bluish-green and blue kornerupines from Kenya and Tanzania, which have been studied since 1972.

Kornerupine Healing Properties

As an often green healing stone, kornerupine’s metaphysical properties reflect the rejuvenating and harmonizing effects of green gemstones. It’s also a great heart chakra stone.

What are the benefits of kornerupine physically?

Physical Healing

Physically, kornerupine is believed to improve vision and boost physical energy.

Emotional Healing

Emotionally, kornerupine is said to:

• Improve communication and eloquence, especially for teaching

• Help you understand that life is sacred

• Balance extreme emotions

• Facilitate personal growth

• Promote unconditional love

Kornerupine Gemstone Properties

Besides rarity, color and size are kornerupine’s top value factors, along with cut, clarity, and transparency.

Color

Most kornerupine stones are murky shades of green or dark brown. However, rarer green shades are attractive and valuable, like light green kornerupine from Kenya or the vibrant emerald-green kornerupine from Tanzania.

Attractive green colors usually come from vanadium, sometimes with chromium and/or iron impurities as well. Darker green specimens usually have more iron. Chromium impurities alone (without vanadium or iron) can also lead to the rare blue kornerupine material from Tanzania and Kenya.

Another value-boosting factor is strong pleochroism.

What is the color change of kornerupine? While the stone doesn’t show the color-changing properties of stones like alexandrite, strong pleochroism can lead to three different colors at different viewing angles.

The strength and colors of the pleochroism can vary based on the stone’s source:

• Madagascar & Sri Lanka: Yellow-brown to brown to green

• Kwale District of Kenya: Bright green to light green to greenish-yellow

• Kenya & Tanzania: Emerald-green to blue-gray to reddish-purple

• Greenland: Dark green to reddish-blue to light blue

Kornerupine can also be colorless or shades of pink, brown, and yellow, but bluish-green and emerald-green gems are most valuable.

Cut

Faceted kornerupines are quite rare because most crystals are small, not gem-quality, or difficult to cut given their distinct cleavage. These factors make faceted kornerupine gems quite valuable. Common faceted cuts are oval, emerald, round, and cushion shapes.

The stone can also be cut into beads or cabochons, the latter of which is necessary for cat’s eye or star kornerupines to properly display their optical effects.

Clarity

Higher clarity means fewer visible inclusions and higher value. Inclusions almost always reduce value, unless they cause optical effects like chatoyancy and asterism.

Other inclusions can include:

• Fractures

• Partially healed fractures (may contain negative crystals and fluid)

• Fluid inclusions in parallel arrangement

• Colorless zircon

• Black or red rutile

• Red-orange hexagonal plates of hematite

• Rounded apatite crystals

• Liquid and liquid-and-gas inclusions

• Elongated quartz and tourmaline (rare)

Larger kornerupines are generally more included than smaller stones.

Carat Weight & Size

Kornerupine’s size ranges broadly, particularly by quality and source. Most gems are under 5 carats.

Many gem-quality kornerupine crystals are small, except some material from Myanmar, Sri Lanka, and East Africa that has yielded 20+ carat gems. Large crystals from Canada (up to 2 cm) and the largest crystals from Greenland (up to 23 cm) either aren’t cuttable or only yield small gems.

Eye-clean stones (no visible inclusions without magnification) are rare over 5 carats.

Among the largest known faceted kornerupine gems are a brown 21.6-carat stone and a golden 16.5-carat stone, both from Sri Lanka. The largest known cat’s eye kornerupine is 7.57 carats.

Price-per-carat rates can increase with larger sizes.

Treatments

Treatments on kornerupine are rarely if ever seen, but the Gemological Institute of America (GIA) did discover the only coated kornerupine they’d ever seen in 2015: kornerupine beads treated with a metallic coating, likely copper.

Kornerupine Formation & Sources

Kornerupine is a metamorphic mineral, and it usually forms when boron-rich sedimentary or volcanic rocks undergo high-grade metamorphism, altering the minerals inside.

The mineral also forms inside metamorphosed anorthosite rocks.

Mining Locations

Where is kornerupine mined? Besides the primary source, Sri Lanka, gem-quality kornerupine is only currently sourced from:

• Australia

• Canada

• Greenland

• Kenya

• Madagascar

• Myanmar

• Tanzania

• South Africa

The sources of optically phenomenal kornerupine varieties are:

• Cat’s Eye: India, Myanmar, Sri Lanka

• Star: Myanmar, Kenya (Taita Hills), Sri Lanka

Kornerupine Price & Value

Kornerupine’s price-per-carat mostly depends on its color and size. Overall, the price for faceted gems can range from around $65 to $120 or higher per carat. A 2-carat stone generally goes for 4- to 5-times more per carat than a 1-carat stone.

On average, faceted kornerupine gem prices by color are:

• Bluish-Green: $120/ct (up to 1 ct); $130/ct (1-3 cts)

• Light Green: $90/ct (up to 1 ct); $100/ct (1-3 cts)

• Medium Yellow-Green: $90/ct (up to 1 ct); $95/ct (1-3 cts)

• Light Yellow-Green: $65/ct (up to 1 ct); $70/ct (1-3 cts)

• Medium Yellow: $80/ct (up to 1 ct); $90/ct (1-3 cts)

• Brownish-Green: $50/ct (up to 1 ct); $110/ct (1-3 cts)

Exceptional faceted specimens can reach $500 per carat or higher.

Regular cabochons generally range from around $40 to $280 per carat. Cat’s eye cabochons can cost anywhere from $10 to $1,200 per carat, with most falling between $20 to $50 per carat.

Kornerupine Care and Maintenance

Luckily, gemstone care for kornerupine is pretty easy. Kornerupine jewelry should have protective settings though, especially rings.

Avoid ultrasonic cleaners. Instead, clean kornerupine with warm water, mild soap, and a soft toothbrush. Store separately from other gems.

Are You Keen on Kornerupine?

Long considered a collector’s stone, more casual gem lovers have come to adore kornerupine. From beautiful earthy hues that can change at different angles to a colorful history in icy Greenland, kornerupine is a fascinating gem any rare gem aficionado will love.

Buy kornerupine gemstones today!