Monteregianite-(Y) is an extremely rare silicate mineral typically found in the alkaline intrusive complexes of the Monteregian Hills. It usually occurs as small, clear to white tabular crystals or radiating sprays embedded within cavities of syenite or pegmatite. It is primarily sought after by advanced collectors of rare species and those focusing on the mineralogy of Mont Saint-Hilaire.
Is this monteregianite-(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 monteregianite-(y) with a known reference. Monteregianite-(Y) sits at Mohs ~3.5, 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 to silky.
- 4Match the color rangeCompare against the expected color range: colorless, greenish, gray, gray white, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, pseudo orthorhombic, radial.
Often confused with
Monteregianite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside monteregianite-(y)
Minerals reported to co-occur with monteregianite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNa₂YSi₈O₁₉·5H₂O
- Mohs hardness
- ~3.5
- Density
- 2.42 g/cm³
- Streak
- White
- Luster
- Vitreous to silky
- Transparency
- Transparent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, pseudo orthorhombic, radial
- Cleavage
- Perfect on {110}, very good on {010}, good to fair on {110}
- Fluorescence
- Green under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities, metamorphosed inclusions, and rheomorphic breccias in nepheline syenite in an intrusive alkalic gabbro-syenite complex
Where rockhounds find monteregianite-(y)
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: In miarolitic cavities, metamorphosed inclusions, and rheomorphic breccias in nepheline syenite in an intrusive alkalic gabbro-syenite complex. If you start seeing calcite, pectolite, microcline in float, you are in the right ground. Typical habit: acicular, pseudo orthorhombic, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify monteregianite-(y)?+
Where is monteregianite-(y) found?+
What rocks look like monteregianite-(y)?+
What minerals are found with monteregianite-(y)?+
What kind of rock does monteregianite-(y) form in?+
What is monteregianite-(y) used for?+
Find monteregianite-(y) on the map
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