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, 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.