Phillipsite is a common zeolite mineral recognized by its distinctive, complex cross-shaped penetration twins. It typically forms within the cavities of volcanic rocks like basalt, often appearing as white or colorless radiating clusters.
Is this phillipsite?
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 phillipsite with a known reference. Phillipsite 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: white, colorless, yellow, red, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: complex cruciform penetration twins, radiating aggregates.
Often confused with
Phillipsite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside phillipsite
Minerals reported to co-occur with phillipsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na,Ca)₁₋₃(Si,Al)₈O₁₆·6H₂O
- Mohs hardness
- 4-5
- Density
- 2.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Complex cruciform penetration twins, radiating aggregates
- Cleavage
- Distinct on {010}
- Rarity
- Common
- Uses
- Collector, Scientific research
- Host rock
- basaltic vugs and cavities
Where rockhounds find phillipsite
Classic worldwide localities
- Sicily, Italy
- Giant's Causeway, Northern Ireland
- Iceland
- Table Mountain, Colorado, USA
- Victoria, Australia
Field-hunting tip
Where it forms: basaltic vugs and cavities. If you start seeing chabazite, natrolite, calcite in float, you are in the right ground. Typical habit: complex cruciform penetration twins, radiating aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify phillipsite?+
Where is phillipsite found?+
What rocks look like phillipsite?+
What minerals are found with phillipsite?+
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What is phillipsite used for?+
Find phillipsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
