Ferrierite-K is a rarer member of the zeolite group often found as thin, bladed crystals or radiating sprays within volcanic cavities. It is most easily identified by its distinct bladed habit and association with other secondary zeolites in basaltic host rocks.
Is this ferrierite-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 ferrierite-k with a known reference. Ferrierite-K sits at Mohs 3-3.5, 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 to silky.
- 4Match the color rangeCompare against the expected color range: white, colorless, pink, orange, red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: radial, tabular.
Often confused with
Ferrierite-K vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ferrierite-k
Minerals reported to co-occur with ferrierite-k. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na)₅(Si₃₁Al₅)O₇₂·18H₂O
- Mohs hardness
- 3-3.5
- Density
- 2.06-2.23 g/cm³
- Streak
- White
- Luster
- Vitreous to silky
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Radial, tabular
- Cleavage
- Perfect on {100}; imperfect on {001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Alteration product of basalts and as a diagenetic material in rhyolitic tuffaceous sediments and in metamorphic rocks
Where rockhounds find ferrierite-k
Classic worldwide localities
- Santa Monica Mountains, California, U.S.A (type locality)
Field-hunting tip
Where it forms: Alteration product of basalts and as a diagenetic material in rhyolitic tuffaceous sediments and in metamorphic rocks. If you start seeing calcite, quartz, heulandite in float, you are in the right ground. Typical habit: radial, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrierite-k?+
Where is ferrierite-k found?+
What rocks look like ferrierite-k?+
What minerals are found with ferrierite-k?+
What kind of rock does ferrierite-k form in?+
What is ferrierite-k used for?+
Find ferrierite-k on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
