Erionite-K is a member of the zeolite group that typically forms as delicate, hair-like fibers or woolly mats in volcanic environments. Collectors should be aware of its asbestiform nature, which requires strict safety protocols to prevent inhalation of hazardous fibers during specimen management.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommonErionite family

Erionite-K

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this erionite-k?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch erionite-k with a known reference. Erionite-K sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Erionite-K leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Erionite-K typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless, pale yellow.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: acicular crystals, fibrous, woolly aggregates.

Often confused with

Erionite-K vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside erionite-k

Minerals reported to co-occur with erionite-k. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: K₂CaMg(Si₁₃Al₅)O₃₆·15H₂O
Mohs hardness: 3.5-4
Density: 2.1 g/cm³
Colors: White Colorless Pale Yellow
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Hexagonal
Crystal habit: Acicular Crystals, Fibrous, Woolly Aggregates
Cleavage: None
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Volcanic Ash Beds, Basalt Cavities
Typical price: $20-100 per specimen

Where rockhounds find erionite-k

Classic worldwide localities

Durkee, Oregon, USA
Jersey Valley, Nevada, USA
Rome, Oregon, USA
Antrim, Northern Ireland

Field-hunting tip

Look in volcanic ash beds, basalt cavities country — that is the host setting where erionite-k typically forms. If you start seeing chabazite, phillipsite, calcite in float, you are in the right ground. Field specimens usually show a acicular crystals, fibrous, woolly aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify erionite-k?+

Mohs hardness is 3.5-4. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless, pale yellow.

Where is erionite-k found?+

Notable localities include Durkee, Oregon, USA; Jersey Valley, Nevada, USA; Rome, Oregon, USA; Antrim, Northern Ireland.

How much is erionite-k worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is erionite-k safe to handle?+

It contains toxic constituents. Erionite is an asbestiform mineral and a known human carcinogen; avoid inhalation of fibers and wear appropriate respiratory protection when handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like erionite-k?+

Erionite-K is most often confused with Offretite, Mordenite, Phillipsite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with erionite-k?+

Erionite-K commonly co-occurs with Chabazite, Phillipsite, Calcite, Montmorillonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does erionite-k form in?+

Erionite-K typically forms in volcanic ash beds, basalt cavities. Working float back to the host body is the standard way to chase a fresh occurrence.

What is erionite-k used for?+

Erionite-K is used in collector, scientific research.

Find erionite-k on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.