Vuoriyarvite-K is a rare titanium-niobium silicate mineral belonging to the labuntsovite group. It typically occurs as small prismatic crystals in alkaline igneous rock environments, often found associated with minerals like aegirine and microcline.
Is this vuoriyarvite-k?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch vuoriyarvite-k with a known reference. Vuoriyarvite-K sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular.
Often confused with
Vuoriyarvite-K vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Labuntsovite is the harder of the two (Mohs 6 vs. 4.5); luster reads vitreous on Vuoriyarvite-K and greasy on Labuntsovite.

How to tell apart: Streak differs, so Vuoriyarvite-K leaves white, Gormanite leaves pale green.

Often found alongside vuoriyarvite-k
Minerals reported to co-occur with vuoriyarvite-k. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na,□)₁₂Nb₈(Si₄O₁₂)₄O₈·12-16H₂O
- Mohs hardness
- 4.5
- Density
- 2.95 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- The mineral formed by the hydrothermal alteration of pyrochlore
Where rockhounds find vuoriyarvite-k
Classic worldwide localities
- Lake Vuoriyarvi and the Vuoriyarvi alkali-ultramafic complex, Kola Peninsula, Russia (type locality)
Field-hunting tip
Where it forms: The mineral formed by the hydrothermal alteration of pyrochlore. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.





