Megacyclite is an extremely rare phyllosilicate mineral typically found in the alkaline pegmatites of the Poudrette quarry at Mont Saint-Hilaire. It is usually recognized as delicate, platy to fan-shaped crystal aggregates that are highly sensitive to dehydration.
Is this megacyclite?
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 megacyclite with a known reference. Megacyclite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Megacyclite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Megacyclite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates.
Often confused with
Megacyclite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside megacyclite
Minerals reported to co-occur with megacyclite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNaSi₉O₁₈(OH)₉·19H₂O
- Mohs hardness
- 2
- Density
- 1.82 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks (nepheline Syenite Pegmatites)
Where rockhounds find megacyclite
Classic worldwide localities
- Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia
Field-hunting tip
Look in alkaline igneous rocks (nepheline syenite pegmatites) country, the host setting where megacyclite typically forms. If you start seeing serandite, pectolite, aegirine in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify megacyclite?+
Where is megacyclite found?+
What rocks look like megacyclite?+
What minerals are found with megacyclite?+
What kind of rock does megacyclite form in?+
What is megacyclite used for?+
Find megacyclite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
