Huangite is a rare calcium-bearing sulfate mineral primarily found in fumarolic environments. Collectors should look for its distinctive yellow, thin platy crystal aggregates often associated with other sulfate minerals.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrareAlunite Supergroup family

Huangite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

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Is this huangite?

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 huangite with a known reference. Huangite sits at Mohs 3-4, 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.
4
Match the color range
Compare against the expected color range: white, yellowish.
5
Look at form & habit
Crystal system: trigonal. Typical habit: platy crystals.

Often confused with

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

How to tell apart: Streak differs, so Huangite leaves white, Jarosite leaves pale yellow; luster reads vitreous on Huangite and subadamantine to vitreous, resinous on fractures on Jarosite.

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Often found alongside huangite

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

All properties

Chemical formula: Ca₀.₅Al₃(SO₄)₂(OH)₆
Mohs hardness: 3-4
Density: 2.80 g/cm³
Colors: White Yellowish
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Trigonal
Crystal habit: Platy crystals
Cleavage: On {0001}, perfect
Rarity: Rare
Uses: Collector
Host rock: A product of acid sulfate hydrothermal alteration of rhyolite tuffs and andesites

Where rockhounds find huangite

Classic worldwide localities

El Indio mine, El Indio-Tambo district, east of La Serena, Coquimbo, Chile
Okumanza, near the Kusatsu-Shirane volcano, Gumma Prefecture, Japan

Field-hunting tip

Where it forms: A product of acid sulfate hydrothermal alteration of rhyolite tuffs and andesites. If you start seeing kaolinite, pyrite, woodhouseite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify huangite?+

Mohs hardness is 3-4. Luster: vitreous. The streak is white. Common colors include white, yellowish.

Where is huangite found?+

Notable localities include El Indio mine, El Indio-Tambo district, east of La Serena, Coquimbo, Chile; Okumanza, near the Kusatsu-Shirane volcano, Gumma Prefecture, Japan.

What rocks look like huangite?+

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

What minerals are found with huangite?+

Huangite commonly co-occurs with Kaolinite, Pyrite, Woodhouseite, Alunite, Natroalunite, Minamiite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does huangite form in?+

Where it forms: A product of acid sulfate hydrothermal alteration of rhyolite tuffs and andesites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is huangite used for?+

Huangite is used in collector.

Find huangite on the map

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