Petersite-(Ce) is a rare member of the mixite group that forms beautiful, needle-like acicular crystals or radial tufts. Collectors primarily seek it for its vibrant yellow to brownish-green pom-pom clusters found within oxidized copper ore zones.

Hardness

~3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareMixite Group family

Petersite-(Ce)

Hardness: ~3.5
Luster: Vitreous
Streak: White
Transparency: Translucent

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Is this petersite-(ce)?

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 petersite-(ce) with a known reference. Petersite-(Ce) sits at Mohs ~3.5, 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.
4
Match the color range
Compare against the expected color range: yellowish green.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: acicular clusters, fibrous tufts, spherical aggregates.

Often confused with

Petersite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.

mineral

Mixite

Mohs 3-4

How to tell apart: Streak differs, so Petersite-(Ce) leaves white, Mixite leaves pale bluish green.

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Often found alongside petersite-(ce)

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

All properties

Chemical formula: Cu₆Ce(PO₄)₃(OH)₆·3H₂O
Mohs hardness: ~3.5
Density: 3.424 g/cm³
Colors: Yellowish green
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Hexagonal
Crystal habit: Acicular clusters, fibrous tufts, spherical aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A rare secondary mineral in weathered granite crossed by veins of milky quartz with a small amount of tourmaline

Where rockhounds find petersite-(ce)

Classic worldwide localities

Luobi, Hainan, China
Piesky, Slovakia
Majuba Hill, Nevada, USA

Field-hunting tip

Where it forms: A rare secondary mineral in weathered granite crossed by veins of milky quartz with a small amount of tourmaline. If you start seeing malachite, chlorite, biotite in float, you are in the right ground. Typical habit: acicular clusters, fibrous tufts, spherical aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify petersite-(ce)?+

Mohs hardness is ~3.5. Luster: vitreous. The streak is white. Common colors include yellowish green.

Where is petersite-(ce) found?+

Notable localities include Luobi, Hainan, China; Piesky, Slovakia; Majuba Hill, Nevada, USA.

Is petersite-(ce) safe to handle?+

Petersite-(Ce) contains copper. Contains copper; wash hands thoroughly after handling and avoid inhaling dust from fibrous aggregates.

What rocks look like petersite-(ce)?+

Petersite-(Ce) is most often confused with Mixite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with petersite-(ce)?+

Petersite-(Ce) commonly co-occurs with Malachite, Chlorite, Biotite, Quartz, Albite, Orthoclase. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does petersite-(ce) form in?+

Where it forms: A rare secondary mineral in weathered granite crossed by veins of milky quartz with a small amount of tourmaline. Working float back to the host body is the standard way to chase a fresh occurrence.

What is petersite-(ce) used for?+

Petersite-(Ce) is used in collector.

Find petersite-(ce) on the map

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