Hendricksite is a rare zinc-bearing member of the mica group, typically identified by its dark, bronzy, micaceous platy crystals. It is primarily found within the unique mineral environment of the Sterling Hill mine in New Jersey. Collectors should look for its distinctive pearly luster and perfect basal cleavage characteristic of the mica family.

Hardness

2.5-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareMica Group family

Hendricksite

Hardness: 2.5-3
Luster: Pearly
Streak: White
Transparency: Translucent

Is this hendricksite?

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 hendricksite with a known reference. Hendricksite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Hendricksite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Hendricksite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: dark brown, reddish brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy, micaceous.

Often confused with

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

Often found alongside hendricksite

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

All properties

Chemical formula: (K,Na)(Zn,Mn,Mg,Fe²⁺)₃(Si₃Al)O₁₀(OH,F)₂
Mohs hardness: 2.5-3
Density: 3.10-3.15 g/cm³
Colors: Dark Brown Reddish Brown
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy, Micaceous
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Metamorphic Zinc Ore Deposits
Typical price: $20-150 thumbnail

Where rockhounds find hendricksite

Classic worldwide localities

Sterling Hill Mine, New Jersey, USA

Field-hunting tip

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

Common questions

How do you identify hendricksite?+

Mohs hardness is 2.5-3. It typically shows a pearly luster. The streak is white. Common colors include dark brown, reddish brown.

Where is hendricksite found?+

Notable localities include Sterling Hill Mine, New Jersey, USA.

How much is hendricksite worth?+

Typical asking prices fall in the range of $20-150 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like hendricksite?+

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

What minerals are found with hendricksite?+

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

What kind of rock does hendricksite form in?+

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

What is hendricksite used for?+

Hendricksite is used in collector.

Find hendricksite on the map

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