Hauckite is a very rare hydrated iron-zinc sulfate mineral typically found as small, yellow, micaceous hexagonal plates. It is almost exclusively known from the Franklin and Sterling Hill mines in New Jersey, where it occurs in association with other zinc-rich minerals in metamorphosed deposits.

Hardness

2.5

Mohs

Luster

Pearly

Streak

Yellow

Transparency

Translucent

mineralrare

Hauckite

Hardness: 2.5
Luster: Pearly
Streak: Yellow
Transparency: Translucent

Is this hauckite?

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 hauckite with a known reference. Hauckite 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. Hauckite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Hauckite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: yellow, brownish-yellow.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: platy crystals, pseudohexagonal rosettes.

Often confused with

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

mineral

Woodwardite

Mohs 1.5-2.5

How to tell apart: Streak differs — Hauckite leaves yellow, Woodwardite leaves white.

How to tell apart: Streak differs — Hauckite leaves yellow, Hydrotalcite leaves white.

Compare →

Often found alongside hauckite

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

All properties

Chemical formula: (Fe³⁺,Mg)₃Zn₃(SO₄)(OH)₈·2H₂O
Mohs hardness: 2.5
Density: 2.8 g/cm³
Colors: Yellow Brownish-yellow
Streak: Yellow
Luster: Pearly
Transparency: Translucent
Crystal system: Hexagonal
Crystal habit: Platy Crystals, Pseudohexagonal Rosettes
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Zinc Ore Deposits
Typical price: $50-300 per specimen

Where rockhounds find hauckite

Classic worldwide localities

Franklin Mining District, New Jersey, USA

Field-hunting tip

Look in metamorphosed zinc ore deposits country — that is the host setting where hauckite typically forms. If you start seeing franklinite, willemite, zincite in float, you are in the right ground. Field specimens usually show a platy crystals, pseudohexagonal rosettes habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hauckite?+

Mohs hardness is 2.5. It typically shows a pearly luster. The streak is yellow. Common colors include yellow, brownish-yellow.

Where is hauckite found?+

Notable localities include Franklin Mining District, New Jersey, USA.

How much is hauckite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like hauckite?+

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

What minerals are found with hauckite?+

Hauckite commonly co-occurs with Franklinite, Willemite, Zincite, Sussexite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hauckite form in?+

Hauckite typically forms in metamorphosed zinc ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hauckite used for?+

Hauckite is used in collector.

Find hauckite on the map

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