Identification guide · Silicate Minerals
How to Identify Nepheline
Nepheline is usually colorless, white, and gray with a vitreous luster and is translucent. It has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Its streak is white. It is most often confused with Feldspar, Leucite, and Microcline; the tests below separate them.
Nepheline identification checklist
| Color | Colorless, White, Gray, Yellowish, Greenish, Reddish | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Poor on {1010} | |
| Fracture | Subconchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.6 | Ordinary rock-like heft (specific gravity about 2.6), similar to quartz. |
| Crystal system | Hexagonal |
Extra tests for Nepheline
Glass check. Nepheline shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Nepheline look-alikes and how to tell them apart
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Nepheline vs Feldspar →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Nepheline vs Leucite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Nepheline vs Microcline →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Nepheline vs Orthoclase →
Field tips
- Look for gray to colorless masses with a greasy luster in silica-poor igneous rocks rather than sharp crystals.
- Nepheline is about 6 in hardness with poor cleavage and a subconchoidal fracture.
- It becomes cloudy and gelatinizes when treated with acid, helping separate it from quartz and feldspar.
Nepheline identification FAQ
How can you tell if a rock is Nepheline?
Check the color (colorless, white, gray, and yellowish), the vitreous luster, a Mohs hardness of 6 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Nepheline?
Nepheline has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is the difference between Nepheline and Feldspar?
Nepheline (Mohs 6, vitreous luster) and Feldspar (Mohs 6–6.5, vitreous to pearly luster) look alike, but hardness, streak and heft usually separate them. See the full Nepheline vs Feldspar comparison for a side-by-side table.
Is Nepheline worth anything?
Entry-level Nepheline specimens sell for around $5, typical collector pieces about $30, and premium examples $150 or more depending on size, quality and locality.
What color is Nepheline?
Nepheline is most often colorless, white, gray, and yellowish. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
