Goslarite is a hydrated zinc sulfate that typically forms as a secondary efflorescence in mines where zinc-rich sulfide ores have oxidized. It is highly unstable in dry air and will rapidly dehydrate into a white powder, so collectors must keep specimens in airtight, humidity-controlled containers to maintain their crystal structure.

Hardness

2-2.5

Mohs

Luster

Vitreous, silky if fibrous

Streak

White

Transparency

Transparent

mineralcommon

Goslarite

Hardness: 2-2.5
Luster: Vitreous, silky if fibrous
Streak: White
Transparency: Transparent

Is this goslarite?

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 goslarite with a known reference. Goslarite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous, silky if fibrous.
4
Match the color range
Compare against the expected color range: colorless, blue, brown, green, green blue.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: acicular, massive, stalactitic.

Often confused with

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

How to tell apart: Streak differs, so Goslarite leaves white, Morenosite leaves pale green to white.

Compare →

Often found alongside goslarite

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

All properties

Chemical formula: ZnSO₄·7H₂O
Mohs hardness: 2-2.5
Density: 1.98 g/cm³
Colors: Colorless Blue Brown Green Green blue
Streak: White
Luster: Vitreous, silky if fibrous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Acicular, massive, stalactitic
Cleavage: On {010}, perfect
Rarity: Common
Uses: Collector
Host rock: A secondary mineral in oxidized portions of zinc sulfide deposits, particularly as coatings on walls of mine passages

Where rockhounds find goslarite

Classic worldwide localities

Bisbee, Cochise Co., Arizona, USA
Central district, Grant Co., New Mexico, USA
Island Mountain, Trinity Co., California, USA
Butte, Silver Bow Co., Montana, USA
Rammelsberg mine, near Goslar, Harz Mountains, and at Freiberg and Altenberg, Saxony, Germany
Baňská Stiavnica (Schemnitz), Slovakia

Field-hunting tip

Where it forms: A secondary mineral in oxidized portions of zinc sulfide deposits, particularly as coatings on walls of mine passages. If you start seeing epsomite, melanterite, pickeringite in float, you are in the right ground. Typical habit: acicular, massive, stalactitic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify goslarite?+

Mohs hardness is 2-2.5. Luster: vitreous, silky if fibrous. The streak is white. Common colors include colorless, blue, brown, green.

Where is goslarite found?+

Notable localities include Bisbee, Cochise Co., Arizona, USA; Central district, Grant Co., New Mexico, USA; Island Mountain, Trinity Co., California, USA; Butte, Silver Bow Co., Montana, USA; Rammelsberg mine, near Goslar, Harz Mountains, and at Freiberg and Altenberg, Saxony, Germany.

Is goslarite safe to handle?+

Contains zinc and sulfates; soluble in water and can cause irritation. Handle with care, avoid ingestion or prolonged skin contact, and store in a sealed container to prevent dehydration and crumbling.

What rocks look like goslarite?+

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

What minerals are found with goslarite?+

Goslarite commonly co-occurs with Epsomite, Melanterite, Pickeringite, Chalcanthite, Gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does goslarite form in?+

Where it forms: A secondary mineral in oxidized portions of zinc sulfide deposits, particularly as coatings on walls of mine passages. Working float back to the host body is the standard way to chase a fresh occurrence.

What is goslarite used for?+

Goslarite is used in collector.

Find goslarite on the map

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