Donnayite-(Y) is an exceedingly rare carbonate mineral typically found in the miarolitic cavities of alkaline complexes. Collectors usually identify it by its pseudo-hexagonal, tabular crystal habit and its occurrence alongside other rare earth element minerals in complex pegmatite environments.
Is this donnayite-(y)?
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 donnayite-(y) with a known reference. Donnayite-(Y) sits at Mohs ~3, 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, brown, brownish yellow, gray, gray white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: pseudo-hexagonal dipyramidal crystals.
Often confused with
Donnayite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Synchysite-(Y) is the harder of the two (Mohs ~4.5 vs. ~3); streak differs, so Donnayite-(Y) leaves white, Synchysite-(Y) leaves brown; luster reads vitreous on Donnayite-(Y) and greasy on Synchysite-(Y).
Often found alongside donnayite-(y)
Minerals reported to co-occur with donnayite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaSr₃CaY(CO₃)₆·3H₂O
- Mohs hardness
- ~3
- Density
- 3.30 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to opaque
- Crystal system
- Triclinic
- Crystal habit
- Pseudo-hexagonal dipyramidal crystals
- Cleavage
- On {001}, fair to imperfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In pegmatite dikes, miarolitic cavities, and interstices in nepheline syenite in an alkaline complex (Mont Saint-Hilaire, Canada)
Where rockhounds find donnayite-(y)
Classic worldwide localities
- Mont Saint-Hilaire, and near Saint-Amable, Quebec, Canada
- Mt. Kukisvumchorr, Khibiny massif, Kola Peninsula, and at the Vishnevogorsk complex, Vishnevy-Ilmen Mountains, Southern Ural Mountains, Russia
Field-hunting tip
Where it forms: In pegmatite dikes, miarolitic cavities, and interstices in nepheline syenite in an alkaline complex (Mont Saint-Hilaire, Canada). If you start seeing ewaldite, mckelveyite-, synchysite in float, you are in the right ground. Typical habit: pseudo-hexagonal dipyramidal crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify donnayite-(y)?+
Where is donnayite-(y) found?+
What rocks look like donnayite-(y)?+
What minerals are found with donnayite-(y)?+
What kind of rock does donnayite-(y) form in?+
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Find donnayite-(y) on the map
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