Serendibite is an exceptionally rare borosilicate mineral prized by collectors for its deep blue to green-blue color. It typically forms in contact metamorphic zones where boron-rich fluids interact with carbonate rocks. Due to its scarcity and refractive indices, it is one of the most expensive and sought-after gems in the mineral world.

Hardness

6.5-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Serendibite

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

Is this serendibite?

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 serendibite with a known reference. Serendibite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: blue, blue green, gray blue, light yellow, dark blue.
5
Look at form & habit
Crystal system: triclinic. Typical habit: granular, twinning common.

Often confused with

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

Often found alongside serendibite

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

All properties

Chemical formula: Ca₄(Mg₆Al₆)O₄[Si₆B₃Al₃O₃₆]
Mohs hardness: 6.5-7
Density: 3.42-3.52 g/cm³
Colors: Blue Blue green Gray blue Light yellow Dark blue
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Granular, twinning common
Cleavage: Good on {010}, {001}; (010) ^ (001) ~66°
Rarity: Rare
Uses: Collector, Gemstone
Host rock: In skarns, affected by boron metasomatism, along the contact between carbonate rocks and granite, tonalite, or granulite

Where rockhounds find serendibite

Classic worldwide localities

Johnsburg, Warren Co., Amity, near Warwick, Orange Co., and Russell, St. Lawrence Co., New York, USA
New City quarry, three km south of Riverside, Riverside Co., California, USA
Gangapitiya, near Ambakotte, Sri Lanka
Melville Peninsula, Northwest Territories, Canada
Tayozhnoye iron deposit, 550 km south of Yakutsk, Yakutia, Russia
Handeni district, Tanzania

Field-hunting tip

Where it forms: In skarns, affected by boron metasomatism, along the contact between carbonate rocks and granite, tonalite, or granulite. If you start seeing diopside, spinel, phlogopite in float, you are in the right ground. Typical habit: granular, twinning common. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify serendibite?+

Mohs hardness is 6.5-7. Luster: vitreous. The streak is white. Common colors include blue, blue green, gray blue, light yellow.

Where is serendibite found?+

Notable localities include Johnsburg, Warren Co., Amity, near Warwick, Orange Co., and Russell, St. Lawrence Co., New York, USA; New City quarry, three km south of Riverside, Riverside Co., California, USA; Gangapitiya, near Ambakotte, Sri Lanka; Melville Peninsula, Northwest Territories, Canada; Tayozhnoye iron deposit, 550 km south of Yakutsk, Yakutia, Russia.

What rocks look like serendibite?+

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

What minerals are found with serendibite?+

Serendibite commonly co-occurs with Diopside, Spinel, Phlogopite, Scapolite, Calcite, Tremolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does serendibite form in?+

Where it forms: In skarns, affected by boron metasomatism, along the contact between carbonate rocks and granite, tonalite, or granulite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is serendibite used for?+

Serendibite is used in collector, gemstone.

Find serendibite on the map

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