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, 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.