Alumotantite is an extremely rare aluminum-tantalum oxide mineral found in highly evolved granite pegmatites. It typically appears as small, colorless to pale yellow, transparent tabular crystals that can be difficult to distinguish from other rare tantalate species without chemical analysis.

Hardness

7.5

Mohs

Luster

Adamantine to greasy

Streak

White

Transparency

Transparent to translucent

mineralrare

Alumotantite

Hardness: 7.5
Luster: Adamantine to greasy
Streak: White
Transparency: Transparent to translucent

Is this alumotantite?

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 alumotantite with a known reference. Alumotantite sits at Mohs 7.5, 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: adamantine to greasy.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals.

Often confused with

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

mineral

Stibiotantalite

Mohs 5.5

How to tell apart: Alumotantite is noticeably harder (Mohs 7.5 vs. 5.5); streak differs, so Alumotantite leaves white, Stibiotantalite leaves pale yellow to yellow-brown; luster reads adamantine to greasy on Alumotantite and resinous to adamantine on Stibiotantalite.

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Often found alongside alumotantite

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

All properties

Chemical formula: AlTaO₄
Mohs hardness: 7.5
Density: 7.48 g/cm³
Colors: Colorless White
Streak: White
Luster: Adamantine to greasy
Transparency: Transparent to translucent
Crystal system: Orthorhombic
Crystal habit: Tabular crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In albitized areas of highly fractionated rare element-enriched granite pegmatites

Where rockhounds find alumotantite

Classic worldwide localities

Mdara mine, Bikita, Zimbabwe
Alto do Giz pegmatite, near Parelhas, Rio Grande do Norte, Brazil

Field-hunting tip

Where it forms: In albitized areas of highly fractionated rare element-enriched granite pegmatites. If you start seeing simpsonite, natrotantite, microlite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify alumotantite?+

Mohs hardness is 7.5. Luster: adamantine to greasy. The streak is white. Common colors include colorless, white.

Where is alumotantite found?+

Notable localities include Mdara mine, Bikita, Zimbabwe; Alto do Giz pegmatite, near Parelhas, Rio Grande do Norte, Brazil.

What rocks look like alumotantite?+

Alumotantite is most often confused with Stibiotantalite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with alumotantite?+

Alumotantite commonly co-occurs with Simpsonite, Natrotantite, Microlite, Cesstibtantite, Sosedkoite, Albite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does alumotantite form in?+

Where it forms: In albitized areas of highly fractionated rare element-enriched granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is alumotantite used for?+

Alumotantite is used in collector.

Find alumotantite on the map

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