Nioboholtite is a rare member of the dumortierite supergroup, chemically distinguished by its significant niobium content. It typically forms as brownish prismatic crystals found within granitic pegmatite environments, often associated with other borosilicate minerals.

Hardness

7-8

Mohs

Streak

White

Transparency

Translucent

mineralrareDumortierite Supergroup family

Nioboholtite

Hardness: 7-8
Streak: White
Transparency: Translucent

No image

Is this nioboholtite?

4-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 nioboholtite with a known reference. Nioboholtite sits at Mohs 7-8, 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
Match the color range
Compare against the expected color range: creamy white, brownish yellow, gray-yellow.
4
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals.

Often confused with

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

How to tell apart: Streak differs, so Nioboholtite leaves white, Holtite leaves light buff.

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Often found alongside nioboholtite

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

All properties

Chemical formula: (Nb₀.₆☐₀.₄)Al₆BSi₃O₁₈
Mohs hardness: 7-8
Density: 3.72 g/cm³
Colors: Creamy whiteBrownish yellowGray-yellow
Streak: White
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Prismatic crystals
Rarity: Rare
Uses: Collector
Host rock: In the internal portion of a complex zoned granitic pegmatite

Where rockhounds find nioboholtite

Classic worldwide localities

Marta mine, northern part of Szklana Hill, Szklary serpentinite massif, ~60 km south of Wroclaw, Lower Silesia, Poland

Field-hunting tip

Where it forms: In the internal portion of a complex zoned granitic pegmatite. If you start seeing holtite, microcline, quartz in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify nioboholtite?+

Mohs hardness is 7-8. The streak is white. Common colors include creamy white, brownish yellow, gray-yellow.

Where is nioboholtite found?+

Notable localities include Marta mine, northern part of Szklana Hill, Szklary serpentinite massif, ~60 km south of Wroclaw, Lower Silesia, Poland.

What rocks look like nioboholtite?+

Nioboholtite is most often confused with Dumortierite, Holtite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with nioboholtite?+

Nioboholtite commonly co-occurs with Holtite, Microcline, Quartz, Muscovite, Spessartine, Chrysoberyl. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does nioboholtite form in?+

Where it forms: In the internal portion of a complex zoned granitic pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is nioboholtite used for?+

Nioboholtite is used in collector.

Find nioboholtite on the map

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