Tounkite is a rare sulfate-rich member of the sodalite group often found in association with silicate-rich metamorphic rocks. It typically displays a pleasant blue hue and is distinguished by its strong fluorescence under short-wave ultraviolet light.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareSodalite Group family

Tounkite

Hardness: 5-5.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this tounkite?

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 tounkite with a known reference. Tounkite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: bottle green, yellow green.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: crystalline.

Often confused with

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

How to tell apart: Streak differs, so Tounkite leaves white, Lazurite leaves bright blue.

How to tell apart: Streak differs, so Tounkite leaves white, Haüyne leaves slightly bluish to colorless.

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Often found alongside tounkite

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

All properties

Chemical formula: (Na,Ca,K)₈(Si₆Al₆)O₂₄(SO₄)₂Cl·0.5H₂O
Mohs hardness: 5-5.5
Density: 2.557 g/cm³
Colors: Bottle greenYellow green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Crystalline
Cleavage: {1010}, fair
Fluorescence: Bright white to yellow under SW UV
Rarity: Rare
Uses: Collector
Host rock: Replacing lazurite in diopside-lazurite rocks (Malo-Bystrinskoye deposit, Russia); in lazurite calciphyres (Tultuy deposit, Russia)

Where rockhounds find tounkite

Classic worldwide localities

Malo-Bystrinskoye and Tultuy lazurite deposits, near Slyudyanka, south of Lake Baikal, Siberia, Russia

Field-hunting tip

Where it forms: Replacing lazurite in diopside-lazurite rocks (Malo-Bystrinskoye deposit, Russia); in lazurite calciphyres (Tultuy deposit, Russia). If you start seeing diopside, lazurite, calcite in float, you are in the right ground. Typical habit: crystalline. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tounkite?+

Mohs hardness is 5-5.5. Luster: vitreous. The streak is white. Common colors include bottle green, yellow green.

Where is tounkite found?+

Notable localities include Malo-Bystrinskoye and Tultuy lazurite deposits, near Slyudyanka, south of Lake Baikal, Siberia, Russia.

What rocks look like tounkite?+

Tounkite is most often confused with Sodalite, Lazurite, Haüyne. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tounkite?+

Tounkite commonly co-occurs with Diopside, Lazurite, Calcite, Pyrite, Apatite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tounkite form in?+

Where it forms: Replacing lazurite in diopside-lazurite rocks (Malo-Bystrinskoye deposit, Russia); in lazurite calciphyres (Tultuy deposit, Russia). Working float back to the host body is the standard way to chase a fresh occurrence.

What is tounkite used for?+

Tounkite is used in collector.

Find tounkite on the map

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