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

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareDumortierite Supergroup family

Nioboholtite

Hardness: 7-8
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this nioboholtite?

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 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. Nioboholtite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Nioboholtite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: brown, yellowish-brown.
5
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.

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: (Al,Mg,☐)Al₄(BSi₃O₁₈)(O,OH)₂
Mohs hardness: 7-8
Density: 3.5-3.6 g/cm³
Colors: Brown Yellowish-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-500 depending on specimen quality

Where rockhounds find nioboholtite

Classic worldwide localities

Madagascar
Austria

Field-hunting tip

Look in granite pegmatites country — that is the host setting where nioboholtite typically forms. If you start seeing quartz, tourmaline, muscovite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify nioboholtite?+

Mohs hardness is 7-8. It typically shows a vitreous luster. The streak is white. Common colors include brown, yellowish-brown.

Where is nioboholtite found?+

Notable localities include Madagascar; Austria.

How much is nioboholtite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen quality. Quality, size, and provenance can move individual specimens well outside that range.

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 Quartz, Tourmaline, Muscovite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does nioboholtite form in?+

Nioboholtite typically forms in granite pegmatites. 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.