Wilancookite is a rare phosphate mineral found in granitic pegmatites. It typically occurs as small, colorless to white equant crystals associated with beryllium and lithium-rich environments.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Wilancookite

Wilancookite is a rare phosphate mineral found in granitic pegmatites. It typically occurs as small, colorless to white equant crystals associated with beryllium and lithium-rich environments.

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

Is this wilancookite?

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 wilancookite with a known reference. Wilancookite 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. Wilancookite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Wilancookite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: cubic. Typical habit: equant crystals.

Often confused with

Wilancookite vs. its common look-alikes — and how to tell them apart in the field.

mineral

Beryllonite

Mohs 5.5-6

How to tell apart: Beryllonite is the harder of the two (Mohs 5.5-6 vs. 3.5).

How to tell apart: Wardite is the harder of the two (Mohs 5 vs. 3.5).

Compare →

Often found alongside wilancookite

Minerals reported to co-occur with wilancookite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Ba,K,Na)₈Li₈Be₂₄P₂₄O₉₆·20H₂O
Mohs hardness: 3.5
Density: 2.42 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Equant Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find wilancookite

Classic worldwide localities

Tip Top mine, Custer, South Dakota, USA

Field-hunting tip

Look in granite pegmatites country — that is the host setting where wilancookite typically forms. If you start seeing quartz, albite, beryllonite in float, you are in the right ground. Field specimens usually show a equant crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify wilancookite?+

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

Where is wilancookite found?+

Notable localities include Tip Top mine, Custer, South Dakota, USA.

How much is wilancookite 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 wilancookite?+

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

What minerals are found with wilancookite?+

Wilancookite commonly co-occurs with Quartz, Albite, Beryllonite, Cookeite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wilancookite form in?+

Wilancookite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is wilancookite used for?+

Wilancookite is used in collector.

Find wilancookite on the map

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