Penkvilksite is a rare titanium-bearing silicate mineral found in the alkaline massifs of the Kola Peninsula. It typically occurs as small, platy, or tabular crystals nestled within pegmatite pockets of igneous complexes.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Penkvilksite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this penkvilksite?

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 penkvilksite with a known reference. Penkvilksite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Penkvilksite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Penkvilksite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless, yellowish-white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals, tabular aggregates.

Often confused with

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

mineral

Steacyite

Mohs 5

How to tell apart: Steacyite is the harder of the two (Mohs 5 vs. 3.5).

How to tell apart: Eudialyte is the harder of the two (Mohs 5-6 vs. 3.5).

Compare →

Often found alongside penkvilksite

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

All properties

Chemical formula: Na₄Ti₂Si₈O₂₂·4H₂O
Mohs hardness: 3.5
Density: 2.44 g/cm³
Colors: White Colorless Yellowish-white
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Platy Crystals, Tabular Aggregates
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Rocks
Typical price: $50-300 per specimen

Where rockhounds find penkvilksite

Classic worldwide localities

Khibiny Massif, Kola Peninsula, Russia
Lovozero Massif, Kola Peninsula, Russia

Field-hunting tip

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

Common questions

How do you identify penkvilksite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless, yellowish-white.

Where is penkvilksite found?+

Notable localities include Khibiny Massif, Kola Peninsula, Russia; Lovozero Massif, Kola Peninsula, Russia.

How much is penkvilksite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like penkvilksite?+

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

What minerals are found with penkvilksite?+

Penkvilksite commonly co-occurs with Aegirine, Kalsilite, Microcline, Nepheline, Titanite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does penkvilksite form in?+

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

What is penkvilksite used for?+

Penkvilksite is used in collector.

Find penkvilksite on the map

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