Aldridgeite is a rare secondary zinc copper sulfate mineral often found as small, delicate, pale blue crystalline crusts in oxidized mine workings. It is primarily known from the Broken Hill ore body and requires careful handling due to its solubility and fragile nature. It is typically sought after by advanced systematic mineral collectors who specialize in rare sulfates.

Hardness

Mohs

Luster

Vitreous

Streak

Pale blue

Transparency

Transparent

mineralrare

Aldridgeite

Hardness: ~3
Luster: Vitreous
Streak: Pale blue
Transparency: Transparent

Is this aldridgeite?

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 aldridgeite with a known reference. Aldridgeite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale blue.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: pale blue.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals, crusts.

Often confused with

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

mineral

Goslarite

Mohs 2-2.5

How to tell apart: Streak differs, so Aldridgeite leaves pale blue, Goslarite leaves white.

How to tell apart: Aldridgeite is noticeably harder (Mohs ~3 vs. 2); streak differs, so Aldridgeite leaves pale blue, Melanterite leaves white.

Compare →

Often found alongside aldridgeite

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

Pyromorphite
mineral · Mohs 3.5-4

All properties

Chemical formula: CdCu₄(SO₄)₂(OH)₆(H₂O)₃
Mohs hardness: ~3
Density: 3.25 g/cm³
Colors: Pale blue
Streak: Pale blue
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Platy crystals, crusts
Cleavage: Perfect on {100} (by analogy to serpierite)
Rarity: Rare
Uses: Collector
Host rock: Secondary mineral in the oxidation zone of a galena, Cd-bearing sphalerite, and chalcopyrite deposit

Where rockhounds find aldridgeite

Classic worldwide localities

Kintore and Block 14 open cuts, Broken Hill, New South Wales, Australia

Field-hunting tip

Where it forms: Secondary mineral in the oxidation zone of a galena, Cd-bearing sphalerite, and chalcopyrite deposit. If you start seeing neidermayrite, pyromorphite in float, you are in the right ground. Typical habit: platy crystals, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify aldridgeite?+

Mohs hardness is ~3. Luster: vitreous. The streak is pale blue. Common colors include pale blue.

Where is aldridgeite found?+

Notable localities include Kintore and Block 14 open cuts, Broken Hill, New South Wales, Australia.

Is aldridgeite safe to handle?+

Aldridgeite contains cadmium and copper and calls for real care. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like aldridgeite?+

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

What minerals are found with aldridgeite?+

Aldridgeite commonly co-occurs with Neidermayrite, Pyromorphite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does aldridgeite form in?+

Where it forms: Secondary mineral in the oxidation zone of a galena, Cd-bearing sphalerite, and chalcopyrite deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is aldridgeite used for?+

Aldridgeite is used in collector.

Find aldridgeite on the map

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