Zincostaurolite is a rare zinc-dominant member of the staurolite group. It is found in metamorphic environments and is visually nearly indistinguishable from common staurolite without chemical analysis.

Hardness

7-7.5

Mohs

Luster

Vitreous to resinous

Streak

White

Transparency

Transparent

mineralrareStaurolite Group family

Zincostaurolite

Hardness: 7-7.5
Luster: Vitreous to resinous
Streak: White
Transparency: Transparent

No image

Is this zincostaurolite?

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 zincostaurolite with a known reference. Zincostaurolite sits at Mohs 7-7.5, 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: vitreous to resinous.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic.

Often confused with

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

mineral

Staurolite

Mohs 7-7.5

How to tell apart: Luster reads vitreous to resinous on Zincostaurolite and subvitreous to resinous on Staurolite.

Often found alongside zincostaurolite

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

All properties

Chemical formula: Zn₂Al₉O₆(SiO₄)₄(O,OH)₂
Mohs hardness: 7-7.5
Density: 3.78 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous to resinous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic
Rarity: Rare
Uses: Collector
Host rock: In metabauxite formed during regional metamorphism

Where rockhounds find zincostaurolite

Classic worldwide localities

Zermatt Valley, Swiss Western Alps, Greece
Island of Samos, Greece

Field-hunting tip

Where it forms: In metabauxite formed during regional metamorphism. If you start seeing kyanite, muscovite, margarite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify zincostaurolite?+

Mohs hardness is 7-7.5. Luster: vitreous to resinous. The streak is white. Common colors include colorless.

Where is zincostaurolite found?+

Notable localities include Zermatt Valley, Swiss Western Alps, Greece; Island of Samos, Greece.

What rocks look like zincostaurolite?+

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

What minerals are found with zincostaurolite?+

Zincostaurolite commonly co-occurs with Kyanite, Muscovite, Margarite, Chloritoid, Gahnite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does zincostaurolite form in?+

Where it forms: In metabauxite formed during regional metamorphism. Working float back to the host body is the standard way to chase a fresh occurrence.

What is zincostaurolite used for?+

Zincostaurolite is used in collector.

Find zincostaurolite on the map

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