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

mineralrare

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.

How to tell apart: Luster reads vitreous on Kostylevite and greasy to vitreous to pearly on Vlasovite.

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: 2.74 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals, Radial Aggregates
Cleavage: {110}; {100}, Perfect
Rarity: Rare
Uses: Collector
Host rock: Alkaline Pegmatites

Where rockhounds find kostylevite

Classic worldwide localities

Khibiny Massif (Russia)
Lovozero Massif (Russia)

Field-hunting tip

Look in alkaline pegmatites country, 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).

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.