Terskite is a rare zirconium silicate mineral discovered in the alkaline massifs of the Kola Peninsula. It typically occurs as pale lilac tabular crystals or fine-grained masses and is most often associated with eudialyte-bearing rocks.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrare

Terskite

Hardness: ~5
Luster: Vitreous
Streak: White
Transparency: Semitransparent

Is this terskite?

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 terskite with a known reference. Terskite sits at Mohs ~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: white, light lilac.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: pseudo tetragonal.

Often confused with

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

How to tell apart: Terskite is noticeably harder (Mohs ~5 vs. ~2); luster reads vitreous on Terskite and pearly, vitreous to dull waxy on Zakharovite.

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Often found alongside terskite

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

All properties

Chemical formula: Na₄ZrSi₆O₁₆·2H₂O
Mohs hardness: ~5
Density: 2.71 g/cm³
Colors: WhiteLight lilac
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Orthorhombic
Crystal habit: Pseudo tetragonal
Cleavage: None
Fluorescence: Yellow-white under SW and LW UV
Rarity: Rare
Uses: Collector
Host rock: In veins in pegmatites in alkalic massifs

Where rockhounds find terskite

Classic worldwide localities

Mts. Alluaiv and Karnasurt, Lovozero massif, and on Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia
Mont Saint-Hilaire and near Saint-Amable, Quebec, Canada

Field-hunting tip

Where it forms: In veins in pegmatites in alkalic massifs. If you start seeing potassic feldspar, sodalite, davyne in float, you are in the right ground. Typical habit: pseudo tetragonal. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify terskite?+

Mohs hardness is ~5. Luster: vitreous. The streak is white. Common colors include white, light lilac.

Where is terskite found?+

Notable localities include Mts. Alluaiv and Karnasurt, Lovozero massif, and on Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia; Mont Saint-Hilaire and near Saint-Amable, Quebec, Canada.

What rocks look like terskite?+

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

What minerals are found with terskite?+

Terskite commonly co-occurs with Potassic feldspar, Sodalite, Davyne, Arfvedsonite, Aegirine, Eudialyte. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does terskite form in?+

Where it forms: In veins in pegmatites in alkalic massifs. Working float back to the host body is the standard way to chase a fresh occurrence.

What is terskite used for?+

Terskite is used in collector.

Find terskite on the map

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