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.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareHopeite Group family

Hillite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this hillite?

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 hillite with a known reference. Hillite 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. Hillite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Hillite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal 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
Colors: White Colorless
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, 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

How do you identify hillite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is hillite found?+

Notable localities include Trench quarry, Churchill, Australia; Santa Lucia mine, Argentina.

How much is hillite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like hillite?+

Hillite is most often confused with Hopeite, Parahopeite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with hillite?+

Hillite commonly co-occurs with Smithsonite, Hemimorphite, Hopeite, Tarbuttite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hillite form in?+

Hillite typically forms in oxidized zinc ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hillite used for?+

Hillite is used in collector.

Find hillite on the map

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