Grenmarite is a rare member of the wöhlerite group primarily found in alkaline igneous environments. It typically forms yellow-to-brown prismatic crystals that are chemically complex and often indistinguishable from related minerals without analytical testing. Collectors generally source this mineral from the specialized pegmatites of the Langesundsfjord region in Norway.
Is this grenmarite?
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 grenmarite with a known reference. Grenmarite 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. Streak: pale yellowish-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellowish brown, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, fibrous.
Often confused with
Grenmarite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside grenmarite
Minerals reported to co-occur with grenmarite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Zr₂Na₂MnZr(Si₂O₇)₂O₂F₂
- Mohs hardness
- 4.5
- Density
- 3.49 g/cm³
- Streak
- Pale yellowish-brown
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, fibrous
- Cleavage
- Good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An early crystallization product, embedded in microcline and fine-grained albite in an alkaline nepheline syenite pegmatite dike cutting larvikite
Where rockhounds find grenmarite
Classic worldwide localities
- Eastern side of the island Vesle Arøya in the Langesundsfjord district, Norway (type locality)
Field-hunting tip
Where it forms: An early crystallization product, embedded in microcline and fine-grained albite in an alkaline nepheline syenite pegmatite dike cutting larvikite. If you start seeing microcline, aegirine, biotite in float, you are in the right ground. Typical habit: aggregates, fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify grenmarite?+
Where is grenmarite found?+
What rocks look like grenmarite?+
What minerals are found with grenmarite?+
What kind of rock does grenmarite form in?+
What is grenmarite used for?+
Find grenmarite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
