Phillipsite-K is a zeolite mineral known for its complex cruciform penetration twinning, often forming radiating 'x-shaped' crystal clusters. It is typically found in the vesicles of basaltic rocks and other volcanic environments where it forms through the alteration of glassy volcanic material.
Is this phillipsite-k?
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-k with a known reference. Phillipsite-K sits at Mohs 4-4.5, 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, reddish white, light yellow, pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, pseudo tetragonal, twinning common.
Often confused with
Phillipsite-K vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside phillipsite-k
Minerals reported to co-occur with phillipsite-k. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₆(Si₁₀Al₆)O₃₂·12H₂O
- Mohs hardness
- 4-4.5
- Density
- 2.20 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, pseudo tetragonal, twinning common
- Cleavage
- {010}, {100}, distinct
- Rarity
- Common
- Uses
- Collector
- Host rock
- Typically in cavities in basalt, of hydrothermal origin; an authigenic mineral in saline lake and hot spring deposits and calcareous deep-sea sediments
Where rockhounds find phillipsite-k
Classic worldwide localities
- Wall Creek, near Monument, and Mount Vernon, Grant Co., Oregon, USA
- Cape Lookout, Tillamook Co., Oregon, USA
- Spray, Wheeler Co., Oregon, USA
- Aci Castello, Sicily, and at Capo di Bove and other localities around Rome, Lazio, Italy
- Annerod, near Giessen, Hesse, and Asbach, Westerwald, Germany
- Giant's Causeway, Co. Antrim, Ireland
Field-hunting tip
Where it forms: Typically in cavities in basalt, of hydrothermal origin; an authigenic mineral in saline lake and hot spring deposits and calcareous deep-sea sediments. If you start seeing zeolites, apophyllite, calcite in float, you are in the right ground. Typical habit: prismatic, pseudo tetragonal, twinning common. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify phillipsite-k?+
Where is phillipsite-k found?+
What rocks look like phillipsite-k?+
What minerals are found with phillipsite-k?+
What kind of rock does phillipsite-k form in?+
What is phillipsite-k used for?+
Find phillipsite-k on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
