Cesplumtantite is a very rare cesium-rich tantalum mineral found in highly evolved granite pegmatites. It typically occurs as small, colorless to pale yellow tabular crystals embedded within or associated with other pegmatite minerals.

Hardness

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Cesplumtantite

Hardness: 7
Luster: Adamantine
Streak: White
Transparency: Transparent

Is this cesplumtantite?

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 cesplumtantite with a known reference. Cesplumtantite sits at Mohs 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: adamantine.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: microscopic crystals.

Often confused with

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

mineral

Pyrochlore

Mohs 5-5.5

How to tell apart: Cesplumtantite is noticeably harder (Mohs 7 vs. 5-5.5); streak differs, so Cesplumtantite leaves white, Pyrochlore leaves brown; luster reads adamantine on Cesplumtantite and vitreous to resinous on Pyrochlore.

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Often found alongside cesplumtantite

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

All properties

Chemical formula: Cs₂Pb₃Ta₈O₂₄
Mohs hardness: 7
Density: 6.87 g/cm³
Colors: Colorless
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Tetragonal
Crystal habit: Microscopic crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In veinlets in a museum specimen from a granite pegmatite

Where rockhounds find cesplumtantite

Classic worldwide localities

Manono pegmatite, Katanga Province, Congo (Shaba Province, Zaire)

Field-hunting tip

Where it forms: In veinlets in a museum specimen from a granite pegmatite. If you start seeing lithiotantite, cassiterite, calciotantite in float, you are in the right ground. Typical habit: microscopic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cesplumtantite?+

Mohs hardness is 7. Luster: adamantine. The streak is white. Common colors include colorless.

Where is cesplumtantite found?+

Notable localities include Manono pegmatite, Katanga Province, Congo (Shaba Province, Zaire).

Is cesplumtantite safe to handle?+

Cesplumtantite contains lead. Contains lead and antimony; wash hands thoroughly after handling and avoid inhaling dust.

What rocks look like cesplumtantite?+

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

What minerals are found with cesplumtantite?+

Cesplumtantite commonly co-occurs with Lithiotantite, Cassiterite, Calciotantite, Microlite, Thoreaulite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cesplumtantite form in?+

Where it forms: In veinlets in a museum specimen from a granite pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cesplumtantite used for?+

Cesplumtantite is used in collector.

Find cesplumtantite on the map

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