Nepheline is a primary feldspathoid mineral found in igneous rocks that are poor in silica. Collectors should look for its characteristic greasy luster on fracture surfaces and its association with other alkaline minerals like aegirine or sodalite.
Is this nepheline?
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 nepheline with a known reference. Nepheline sits at Mohs 5.5-6, 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 greasy.
- 4Match the color rangeCompare against the expected color range: white, gray, yellowish, reddish, brownish, brown, brownish gray, reddish white.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: massive, prismatic.
Often confused with
Nepheline vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside nepheline
Minerals reported to co-occur with nepheline. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,K)AlSiO₄
- Mohs hardness
- 5.5-6
- Density
- 2.55-2.66 g/cm³
- Streak
- White
- Luster
- Vitreous to greasy
- Transparency
- Transparent to nearly opaque, from inclusions or alteration
- Crystal system
- Hexagonal
- Crystal habit
- Massive, prismatic
- Cleavage
- Poor on {1010}, {0001}
- Rarity
- Common
- Uses
- Collector, Industrial
- Host rock
- Characteristic of alkalic rocks as nepheline syenites and gneisses, alkalic gabbros; in sodium-rich hypabyssal rocks, tuffs and lavas, and pegmatites; as a product of sodium metasomatism
Where rockhounds find nepheline
2 mapped spotsClassic worldwide localities
- Litchfield, Kennebec Co., Maine, USA
- Magnet Cove, Hot Spring Co., and on Granite Mountain, near Little Rock, Pulaski Co., Arkansas, USA
- Iron Hill, Gunnison Co., Colorado, USA
- Point of Rocks, Colfax Co., New Mexico, USA
- Vesuvius and Monte Somma, Campania, Italy
- Katzenbuckel, Odenwald, Baden-Württemberg, Germany
Field-hunting tip
Where it forms: Characteristic of alkalic rocks as nepheline syenites and gneisses, alkalic gabbros; in sodium-rich hypabyssal rocks, tuffs and lavas, and pegmatites; as a product of sodium metasomatism. If you start seeing potassic feldspar, plagioclase, sodic pyroxenes in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Arkansas. Start trip planning there.
Common questions
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Find nepheline on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
