Rankachite is a rare tungsten mineral typically found as small, bright yellow to yellowish-green platy crystals. It is most often discovered in weathered hydrothermal veins associated with other tungsten-bearing species.

Hardness

~2.5

Mohs

Luster

Subadamantine to resinous, may be dull

Streak

Brown

Transparency

Opaque to translucent

mineralrare

Rankachite

Hardness: ~2.5
Luster: Subadamantine to resinous, may be dull
Streak: Brown
Transparency: Opaque to translucent

Is this rankachite?

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 rankachite with a known reference. Rankachite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: brown.
3
Read the luster
Hold the specimen under a strong light. Luster: subadamantine to resinous, may be dull.
4
Match the color range
Compare against the expected color range: brownish yellow, dark brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular, encrustations, rosette.

Often confused with

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

mineral

Anthoinite

Mohs 1

How to tell apart: Rankachite is noticeably harder (Mohs ~2.5 vs. 1); streak differs, so Rankachite leaves brown, Anthoinite leaves white; luster reads subadamantine to resinous, may be dull on Rankachite and dull on Anthoinite.

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Often found alongside rankachite

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

All properties

Chemical formula: Ca₀.₅(V⁴⁺,V⁵⁺)(W⁶⁺,Fe³⁺)₂O₈(OH)·2H₂O
Mohs hardness: ~2.5
Density: 4.5 g/cm³
Colors: Brownish yellow Dark brown
Streak: Brown
Luster: Subadamantine to resinous, may be dull
Transparency: Opaque to translucent
Crystal system: Monoclinic
Crystal habit: Acicular, encrustations, rosette
Cleavage: One direction, good, parallel to the plane of flattening
Rarity: Rare
Uses: Collector
Host rock: An alteration product of scheelite and iron sulfides in the oxidation zone of a hydrothermal base-metal deposit

Where rockhounds find rankachite

Classic worldwide localities

Clara Mine, Wofach, Rankach Valley, Schwarzwald, Balden-Wurttenberg, Germany (type locality)

Field-hunting tip

Where it forms: An alteration product of scheelite and iron sulfides in the oxidation zone of a hydrothermal base-metal deposit. If you start seeing scheelite, pyrite, marcasite in float, you are in the right ground. Typical habit: acicular, encrustations, rosette. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rankachite?+

Mohs hardness is ~2.5. Luster: subadamantine to resinous, may be dull. The streak is brown. Common colors include brownish yellow, dark brown.

Where is rankachite found?+

Notable localities include Clara Mine, Wofach, Rankach Valley, Schwarzwald, Balden-Wurttenberg, Germany (type locality).

Is rankachite safe to handle?+

Rankachite contains vanadium. Contains tungsten and iron. Always wash hands after handling to avoid ingestion of fine particles.

What rocks look like rankachite?+

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

What minerals are found with rankachite?+

Rankachite commonly co-occurs with Scheelite, Pyrite, Marcasite, Fluorite, Barite, Ferritungstite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rankachite form in?+

Where it forms: An alteration product of scheelite and iron sulfides in the oxidation zone of a hydrothermal base-metal deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rankachite used for?+

Rankachite is used in collector.

Find rankachite on the map

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