Cryptophyllite is a rare hydrated potassium calcium silicate found primarily in alkaline igneous rocks like nepheline syenites. It typically occurs as small tabular crystals or crusts and is best identified by its association with unique minerals in the Kola Peninsula massifs.
Is this cryptophyllite?
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 cryptophyllite with a known reference. Cryptophyllite 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.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, aggregates.
Often confused with
Cryptophyllite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside cryptophyllite
Minerals reported to co-occur with cryptophyllite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Ca[Si₄O₁₀]·5H₂O
- Mohs hardness
- 3.5
- Density
- 2.185 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage hydrothermal mineral along fractures in a high-potassium peralkaline pegmatite in urtite rocks near the contact with nepheline-apatite rock
Where rockhounds find cryptophyllite
Classic worldwide localities
- Central mine, Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: A late-stage hydrothermal mineral along fractures in a high-potassium peralkaline pegmatite in urtite rocks near the contact with nepheline-apatite rock. If you start seeing shlykovite in float, you are in the right ground. Typical habit: tabular crystals, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cryptophyllite?+
Where is cryptophyllite found?+
What rocks look like cryptophyllite?+
What minerals are found with cryptophyllite?+
What kind of rock does cryptophyllite form in?+
What is cryptophyllite used for?+
Find cryptophyllite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
