Boyleite is a rare secondary zinc sulfate mineral typically found as white crusts or efflorescences in the oxidized zones of zinc-rich sulfide deposits. It is structurally related to the Gunningite group and is highly water-soluble, making it a challenge for collectors to preserve in humid environments. It is most commonly identified by its occurrence as a late-stage weathering product in mines.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareGunningite Group family

Boyleite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this boyleite?

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 boyleite with a known reference. Boyleite 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. Boyleite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Boyleite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: crusts, efflorescences, granular.

Often confused with

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

Often found alongside boyleite

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

All properties

Chemical formula: (Zn,Mg)SO₄·4H₂O
Mohs hardness: 2.5
Density: 3.17 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Crusts, Efflorescences, Granular
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Oxidized Hydrothermal Ore Deposits
Typical price: $20-100 for small specimens

Where rockhounds find boyleite

Classic worldwide localities

Tsumeb, Namibia
Sterling Hill, New Jersey, USA
Galena, Kansas, USA

Field-hunting tip

Look in oxidized hydrothermal ore deposits country — that is the host setting where boyleite typically forms. If you start seeing smithsonite, sphalerite, anglesite in float, you are in the right ground. Field specimens usually show a crusts, efflorescences, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify boyleite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is boyleite found?+

Notable localities include Tsumeb, Namibia; Sterling Hill, New Jersey, USA; Galena, Kansas, USA.

How much is boyleite worth?+

Typical asking prices fall in the range of $20-100 for small specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like boyleite?+

Boyleite is most often confused with Gunningite, Epsomite, Goslarite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with boyleite?+

Boyleite commonly co-occurs with Smithsonite, Sphalerite, Anglesite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does boyleite form in?+

Boyleite typically forms in oxidized hydrothermal ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is boyleite used for?+

Boyleite is used in collector.

Find boyleite on the map

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