Tacharanite is a rare calcium silicate mineral typically found as white, platy, or scaly aggregates within basalt cavities. It is often discovered in association with other zeolite-group minerals and calcium silicates in altered volcanic environments. Collectors prize it for its specific paragenesis within restricted geological sites like the Isle of Skye.

Hardness

3-4

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Tacharanite

Hardness: 3-4
Luster: Pearly
Streak: White
Transparency: Translucent

Is this tacharanite?

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

Often confused with

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

Often found alongside tacharanite

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

All properties

Chemical formula: Ca₁₂Al₂Si₁₈O₅₇(OH)₁₀·~4H₂O
Mohs hardness: 3-4
Density: 2.45 g/cm³
Colors: White Colorless Pale Yellow
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy Aggregates, Scaly Masses
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Basaltic Volcanic Rocks
Typical price: $20-100 per specimen

Where rockhounds find tacharanite

Classic worldwide localities

Skye, Scotland
Antrim, Northern Ireland
Fuka, Japan

Field-hunting tip

Look in basaltic volcanic rocks country, the host setting where tacharanite typically forms. If you start seeing tobermorite, gyrolite, calcite 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 tacharanite?+

Mohs hardness is 3-4. It typically shows a pearly luster. The streak is white. Common colors include white, colorless, pale yellow.

Where is tacharanite found?+

Notable localities include Skye, Scotland; Antrim, Northern Ireland; Fuka, Japan.

How much is tacharanite 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 tacharanite?+

Tacharanite is most often confused with Tobermorite, Gyrolite, Okenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tacharanite?+

Tacharanite commonly co-occurs with Tobermorite, Gyrolite, Calcite, Zeolites. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tacharanite form in?+

Tacharanite typically forms in basaltic volcanic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tacharanite used for?+

Tacharanite is used in collector.

Find tacharanite on the map

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