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, 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.