Hillite is a rare phosphate mineral in the hopeite group that occurs in oxidized zinc deposits. It typically forms small, clear, tabular crystals or radiating sprays that are visually indistinguishable from hopeite without X-ray diffraction analysis.
Is this hillite?
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 hillite with a known reference. Hillite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Hillite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Hillite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, radiating aggregates.
Often confused with
Hillite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside hillite
Minerals reported to co-occur with hillite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Zn(PO₄)₂·2H₂O
- Mohs hardness
- 3.5
- Density
- 3.08 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals, Radiating Aggregates
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zinc Ore Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find hillite
Classic worldwide localities
- Trench quarry, Churchill, Australia
- Santa Lucia mine, Argentina
Field-hunting tip
Look in oxidized zinc ore deposits country — that is the host setting where hillite typically forms. If you start seeing smithsonite, hemimorphite, hopeite in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find hillite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
