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. Phillipsite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Phillipsite typically shows a vitreous luster.
- 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
- Typical price
- $5-30 per specimen
Where rockhounds find phillipsite
Classic worldwide localities
- Sicily, Italy
- Giant's Causeway, Northern Ireland
- Iceland
- Table Mountain, Colorado, USA
- Victoria, Australia
Field-hunting tip
Look in basaltic vugs and cavities country, the host setting where phillipsite typically forms. If you start seeing chabazite, natrolite, calcite in float, you are in the right ground. Field specimens usually show a complex cruciform penetration twins, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find phillipsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
