Tobelite is a rare ammonium-bearing mica that commonly forms in low-temperature hydrothermal environments associated with organic-rich sediments. It is often visually indistinguishable from muscovite or illite, requiring X-ray diffraction or chemical analysis for positive identification.

Hardness

2-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareMica Group family

Tobelite

Hardness: 2-3
Luster: Pearly
Streak: White
Transparency: Translucent

Is this tobelite?

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 tobelite with a known reference. Tobelite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tobelite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Tobelite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, colorless, grayish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy aggregates, scaly masses.

Often confused with

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

Often found alongside tobelite

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

All properties

Chemical formula: (NH₄)Al₂(Si₃Al)O₁₀(OH)₂
Mohs hardness: 2-3
Density: 2.7-2.8 g/cm³
Colors: White Colorless Grayish
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy Aggregates, Scaly Masses
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Clay Deposits, Coal-bearing Sedimentary Rocks
Typical price: $20-100 per specimen

Where rockhounds find tobelite

Classic worldwide localities

Toba, Japan
Coal measures, Czech Republic

Field-hunting tip

Look in hydrothermal clay deposits, coal-bearing sedimentary rocks country — that is the host setting where tobelite typically forms. If you start seeing quartz, kaolinite, pyrophyllite in float, you are in the right ground. Field specimens usually show a platy aggregates, scaly masses habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tobelite?+

Mohs hardness is 2-3. It typically shows a pearly luster. The streak is white. Common colors include white, colorless, grayish.

Where is tobelite found?+

Notable localities include Toba, Japan; Coal measures, Czech Republic.

How much is tobelite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like tobelite?+

Tobelite is most often confused with Muscovite, Illite, Paragonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tobelite?+

Tobelite commonly co-occurs with Quartz, Kaolinite, Pyrophyllite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tobelite form in?+

Tobelite typically forms in hydrothermal clay deposits, coal-bearing sedimentary rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tobelite used for?+

Tobelite is used in collector.

Find tobelite on the map

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