Torreyite is a rare secondary mineral typically found as small, bluish white to colorless, platy or radiating crystals. It is most famous from the zinc mines of Franklin and Sterling Hill, New Jersey, where it forms in oxidized zones of ore bodies.
Is this torreyite?
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 torreyite with a known reference. Torreyite sits at Mohs 3, 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: vitreous to almost pearly, dull.
- 4Match the color rangeCompare against the expected color range: bluish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates, crusts.
Often confused with
Torreyite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Torreyite leaves white, Serpierite leaves greenish white.
How to tell apart: Luster reads vitreous to almost pearly, dull on Torreyite and pearly, silky to dull or earthy in aggregates on Hydrozincite.
Often found alongside torreyite
Minerals reported to co-occur with torreyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₉Zn₄(SO₄)₂(OH)₂₂·8H₂O
- Mohs hardness
- 3
- Density
- 2.665 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to almost pearly, dull
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, radial aggregates, crusts
- Cleavage
- {010}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Very rare, in veinlets cutting calcite–franklinite–willemite ore in a metamorphosed stratiform zinc orebody
Where rockhounds find torreyite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: Very rare, in veinlets cutting calcite–franklinite–willemite ore in a metamorphosed stratiform zinc orebody. If you start seeing mooreite, fluoborite, pyrochroite in float, you are in the right ground. Typical habit: platy crystals, radial aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify torreyite?+
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Find torreyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
