Offretite is a rare zeolite mineral that forms distinctive hexagonal prismatic crystals. It is most commonly found in the vugs or cavities of volcanic basalt flows, often associated with other zeolites like levyne.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareZeolite Group family

Offretite

Hardness: 4
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this offretite?

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 offretite with a known reference. Offretite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Offretite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Offretite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless, yellowish.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: prismatic crystals, radial aggregates.

Often found alongside offretite

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

All properties

Chemical formula: (K,Ca,Na)₂(Si,Al)₁₈O₃₆·14H₂O
Mohs hardness: 4
Density: 2.13 g/cm³
Colors: White Colorless Yellowish
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Prismatic Crystals, Radial Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Basaltic Cavities
Typical price: $20-150 thumbnail

Where rockhounds find offretite

Classic worldwide localities

Mount Simi, Oregon, USA
Col de la Dichere, France
Cape Blomidon, Nova Scotia, Canada
Antrim, Northern Ireland

Field-hunting tip

Look in basaltic cavities country — that is the host setting where offretite typically forms. If you start seeing levyne, chabazite, phillipsite in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify offretite?+

Mohs hardness is 4. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless, yellowish.

Where is offretite found?+

Notable localities include Mount Simi, Oregon, USA; Col de la Dichere, France; Cape Blomidon, Nova Scotia, Canada; Antrim, Northern Ireland.

How much is offretite worth?+

Typical asking prices fall in the range of $20-150 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with offretite?+

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

What kind of rock does offretite form in?+

Offretite typically forms in basaltic cavities. Working float back to the host body is the standard way to chase a fresh occurrence.

What is offretite used for?+

Offretite is used in collector.

Find offretite on the map

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