Lileyite is a very rare barium-rich member of the mica group found primarily in alkaline intrusive complexes. It typically appears as small tabular crystals embedded within nepheline syenite or associated alkaline rocks, often requiring micro-analysis for definitive identification due to its similarity to common biotite.

Hardness

2.5-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareMica Group family

Lileyite

Hardness: 2.5-3
Luster: Pearly
Streak: White
Transparency: Translucent

Is this lileyite?

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 lileyite with a known reference. Lileyite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Lileyite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Lileyite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: dark brown, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often confused with

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

Often found alongside lileyite

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

All properties

Chemical formula: BaFe²⁺₄Mg₂Fe³⁺(Si₄Al₂O₁₈)O₂(OH)₂
Mohs hardness: 2.5-3
Density: 3.39 g/cm³
Colors: Dark Brown Black
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Rocks
Typical price: n/a

Where rockhounds find lileyite

Classic worldwide localities

Khibiny Massif, Russia
Murun Massif, Russia

Field-hunting tip

Look in alkaline igneous rocks country — that is the host setting where lileyite typically forms. If you start seeing aegirine, nepheline, k-feldspar in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify lileyite?+

Mohs hardness is 2.5-3. It typically shows a pearly luster. The streak is white. Common colors include dark brown, black.

Where is lileyite found?+

Notable localities include Khibiny Massif, Russia; Murun Massif, Russia.

How much is lileyite worth?+

Typical asking prices fall in the range of n/a. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like lileyite?+

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

What minerals are found with lileyite?+

Lileyite commonly co-occurs with Aegirine, Nepheline, K-feldspar. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does lileyite form in?+

Lileyite typically forms in alkaline igneous rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is lileyite used for?+

Lileyite is used in collector.

Find lileyite on the map

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