Prismatine is a rare borosilicate mineral that is structurally related to kornerupine, often requiring advanced analytical techniques to distinguish between the two. Collectors usually find it as prismatic to acicular crystals in high-grade metamorphic rocks like granulites or boron-rich metamorphic deposits.

Hardness

6.5-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Prismatine

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

Is this prismatine?

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 prismatine with a known reference. Prismatine 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. Prismatine leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Prismatine typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: green, brown, blue, yellow, white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals, massive, fibrous.

Often confused with

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

Often found alongside prismatine

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

All properties

Chemical formula: (Mg,Fe²⁺,Al)₅(Al,Mg)₁₂(Si,B,Al)₅O₂₁(OH,F)
Mohs hardness: 6.5-7
Density: 3.3-3.4 g/cm³
Colors: Green Brown Blue Yellow White
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals, Massive, Fibrous
Cleavage: Good in One Direction
Rarity: Rare
Uses: Collector, Gemstone
Host rock: Metamorphic Rocks
Typical price: $50-500 per gram for gem quality

Where rockhounds find prismatine

Classic worldwide localities

Madagascar
Sri Lanka
Greenland
Kenya
Canada

Field-hunting tip

Look in metamorphic rocks country — that is the host setting where prismatine typically forms. If you start seeing sillimanite, garnet, cordierite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, fibrous habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify prismatine?+

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

Where is prismatine found?+

Notable localities include Madagascar; Sri Lanka; Greenland; Kenya; Canada.

How much is prismatine worth?+

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

What rocks look like prismatine?+

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

What minerals are found with prismatine?+

Prismatine commonly co-occurs with Sillimanite, Garnet, Cordierite, Kyanite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does prismatine form in?+

Prismatine typically forms in metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is prismatine used for?+

Prismatine is used in collector, gemstone.

Find prismatine on the map

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