Kornerupine is a rare borosilicate mineral that forms elongated, prismatic crystals in high-grade metamorphic rocks. Collectors prize it for its unique color range, especially the rare blue-green hues, and its strong pleochroism which can shift from yellow-brown to green.

Hardness

6.5-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Kornerupine

Hardness: 6.5-7
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this kornerupine?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch kornerupine with a known reference. Kornerupine sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kornerupine leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Kornerupine typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: green, yellowish-green, brown, blue, colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals, fibrous, massive.

Often confused with

Kornerupine vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside kornerupine

Minerals reported to co-occur with kornerupine. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Mg,Fe²⁺)₄(Al,Fe³⁺)₆(SiO₄,BO₄)₅(OH,O)₂
Mohs hardness: 6.5-7
Density: 3.27-3.48 g/cm³
Colors: Green Yellowish-green Brown Blue Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals, Fibrous, Massive
Cleavage: Distinct in One Direction
Rarity: Rare
Uses: Gemstone, Collector
Host rock: Metamorphic Rocks Rich in Aluminum and Magnesium, Such as Granulites
Typical price: $50-500 per carat for gem quality, $20-150 for specimens

Where rockhounds find kornerupine

Classic worldwide localities

Sri Lanka
Madagascar
Tanzania
Canada
Myanmar

Field-hunting tip

Look in metamorphic rocks rich in aluminum and magnesium, such as granulites country, the host setting where kornerupine typically forms. If you start seeing sapphire, spinel, garnet in float, you are in the right ground. Field specimens usually show a prismatic crystals, fibrous, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kornerupine?+

Mohs hardness is 6.5-7. It typically shows a vitreous luster. The streak is white. Common colors include green, yellowish-green, brown, blue.

Where is kornerupine found?+

Notable localities include Sri Lanka; Madagascar; Tanzania; Canada; Myanmar.

How much is kornerupine worth?+

Typical asking prices fall in the range of $50-500 per carat for gem quality, $20-150 for specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like kornerupine?+

Kornerupine is most often confused with Tourmaline, Andalusite, Enstatite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with kornerupine?+

Kornerupine commonly co-occurs with Sapphire, Spinel, Garnet, Cordierite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kornerupine form in?+

Kornerupine typically forms in metamorphic rocks rich in aluminum and magnesium, such as granulites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kornerupine used for?+

Kornerupine is used in gemstone, collector.

Find kornerupine on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.