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

Transparent

mineralrare

Prismatine

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

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. 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: yellow brown, green brown, brown green.
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: 3.341-3.345 g/cm³
Colors: Yellow brownGreen brownBrown green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Prismatic crystals, massive, fibrous
Cleavage: Perfect on {110}
Rarity: Rare
Uses: Collector, Gemstone
Host rock: Metamorphism of boron rich clay sediments to granulite facies

Where rockhounds find prismatine

Classic worldwide localities

Waldheim, Sachsen (Saxony), Germany (type locality)

Field-hunting tip

Where it forms: Metamorphism of boron rich clay sediments to granulite facies. If you start seeing sillimanite, garnet, cordierite in float, you are in the right ground. Typical habit: prismatic crystals, massive, fibrous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify prismatine?+

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

Where is prismatine found?+

Notable localities include Waldheim, Sachsen (Saxony), Germany (type locality).

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?+

Where it forms: Metamorphism of boron rich clay sediments to granulite facies. 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.