Cassidyite is a rare phosphate mineral found in oxidized nickel-rich environments. Collectors typically look for its distinctive pale green, tabular crystals often occurring in radiating clusters or thin crusts.
Is this cassidyite?
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 cassidyite with a known reference. Cassidyite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cassidyite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cassidyite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates, crusts.
Often confused with
Cassidyite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside cassidyite
Minerals reported to co-occur with cassidyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaNi₂(PO₄)₂(OH)₂·2H₂O
- Mohs hardness
- 4
- Density
- 2.85 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Radiating Aggregates, Crusts
- Cleavage
- Good On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Nickel-bearing Hydrothermal Veins and Oxidized Zones of Ore Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find cassidyite
Classic worldwide localities
- Woods Mine, Pennsylvania, USA
- Santa Eulalia District, Mexico
- Reaphook Hill, Australia
Field-hunting tip
Look in nickel-bearing hydrothermal veins and oxidized zones of ore deposits country, the host setting where cassidyite typically forms. If you start seeing goethite, annabergite, schorl in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cassidyite?+
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Find cassidyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
