Kostylevite is a rare zirconium silicate mineral discovered in the alkaline massifs of the Kola Peninsula. It typically occurs as small, colorless prismatic crystals found within pegmatite veins associated with eudialyte-group minerals.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrarenull family

Kostylevite

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

Is this kostylevite?

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 kostylevite with a known reference. Kostylevite 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. Kostylevite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Kostylevite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, radial aggregates.

Often confused with

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

Often found alongside kostylevite

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

All properties

Chemical formula: K₄Zr₂Si₆O₁₈·2H₂O
Mohs hardness: 5
Density: 2.44 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals, Radial Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Alkaline Pegmatites
Typical price: $50-300+ depending on specimen quality

Where rockhounds find kostylevite

Classic worldwide localities

Khibiny Massif (Russia)
Lovozero Massif (Russia)

Field-hunting tip

Look in alkaline pegmatites country — that is the host setting where kostylevite typically forms. If you start seeing eudialyte, aegirine, nepheline in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kostylevite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is kostylevite found?+

Notable localities include Khibiny Massif (Russia); Lovozero Massif (Russia).

How much is kostylevite worth?+

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

What rocks look like kostylevite?+

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

What minerals are found with kostylevite?+

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

What kind of rock does kostylevite form in?+

Kostylevite typically forms in alkaline pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kostylevite used for?+

Kostylevite is used in collector.

Find kostylevite on the map

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