Petersite-(Y) is a rare yttrium-dominant member of the mixite group that typically forms striking, delicate fibrous tufts or spherical aggregates. Collectors look for its characteristic mustard-yellow to greenish-yellow color, often occurring on or within quartz vugs.
Is this petersite-(y)?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch petersite-(y) with a known reference. Petersite-(Y) sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: highly vitreous on {1010} to dull on {0001}.
- 4Match the color rangeCompare against the expected color range: yellow green.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic, radial.
Often confused with
Petersite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside petersite-(y)
Minerals reported to co-occur with petersite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₆Y(PO₄)₃(OH)₆·3H₂O
- Mohs hardness
- 3-4
- Density
- 3.41 g/cm³
- Colors
- Streak
- White
- Luster
- Highly vitreous on {1010} to dull on {0001}
- Transparency
- Semitransparent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic, radial
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare secondary mineral in biotite-plagioclase hornfels near a diabase stock cutting Triassic sediments (Laurel Hill, New Jersey, USA)
Where rockhounds find petersite-(y)
Classic worldwide localities
- Laurel Hill, Secaucas, Hudson Co., New Jersey, USA
- Herrensegen mine, near Schapbach, and the Silberbrünnle mine, near Gengenbach (Nd-rich), Black Forest, Germany
- Sa Duchessa mine, Oridda district, Sardinia
- Hanama quarry, Hai-Yama, Shiga Prefecture, Japan
Field-hunting tip
Where it forms: A very rare secondary mineral in biotite-plagioclase hornfels near a diabase stock cutting Triassic sediments (Laurel Hill, New Jersey, USA). If you start seeing chalcopyrite, malachite, chrysocolla in float, you are in the right ground. Typical habit: prismatic, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify petersite-(y)?+
Where is petersite-(y) found?+
Is petersite-(y) safe to handle?+
What rocks look like petersite-(y)?+
What minerals are found with petersite-(y)?+
What kind of rock does petersite-(y) form in?+
What is petersite-(y) used for?+
Find petersite-(y) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
