Keiviite-(Yb) is a very rare silicate mineral typically found as small, colorless to white tabular crystals. It is primarily known from specific alkaline pegmatite environments, most notably in the Keivy Massif of Russia, and is highly sought after by advanced systematic mineral collectors.
Is this keiviite-(yb)?
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 keiviite-(yb) with a known reference. Keiviite-(Yb) 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: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular to prismatic crystals.
Often confused with
Keiviite-(Yb) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Thortveitite is the harder of the two (Mohs 6-7 vs. 4-5); streak differs, so Keiviite-(Yb) leaves white, Thortveitite leaves gray.
How to tell apart: Gadolinite-(Y) is the harder of the two (Mohs 6.5-7 vs. 4-5); streak differs, so Keiviite-(Yb) leaves white, Gadolinite-(Y) leaves greenish gray.
Often found alongside keiviite-(yb)
Minerals reported to co-occur with keiviite-(yb). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Yb₂Si₂O₇
- Mohs hardness
- 4-5
- Density
- 5.95 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular to prismatic crystals
- Cleavage
- Perfect on {110}, imperfect on {001}
- Fluorescence
- Faint green under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In microcline-bearing pegmatites; two generations of the mineral are present
Where rockhounds find keiviite-(yb)
Classic worldwide localities
- Mt. Ploskaya, Keivy massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: In microcline-bearing pegmatites; two generations of the mineral are present. If you start seeing fluorite, bastnäsite, hingganite in float, you are in the right ground. Typical habit: tabular to prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify keiviite-(yb)?+
Where is keiviite-(yb) found?+
What rocks look like keiviite-(yb)?+
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Find keiviite-(yb) on the map
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