Identification guide · Silicate Minerals
How to Identify Leucite
Leucite is usually white, gray, and colorless with a vitreous luster and is translucent. It has a Mohs hardness of 5.75. 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 Nepheline, Orthoclase, and Microcline; the tests below separate them.
Leucite identification checklist
| Color | White, Gray, Colorless, Pale yellow | 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 | 5.75 | 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 | Very poor | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.5 | Ordinary rock-like heft (specific gravity about 2.5), similar to quartz. |
| Crystal system | Tetragonal |
Extra tests for Leucite
Glass check. Leucite 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.
Leucite look-alikes and how to tell them apart
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Leucite vs Nepheline →
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Leucite vs Orthoclase →
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Leucite vs Microcline →
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for rounded, near-spherical pale crystals with a trapezohedral form set in dark volcanic rock.
- Leucite is moderately hard, has very poor cleavage, and a conchoidal fracture.
- Distinguish it from garnet by its lower hardness and volcanic host, and from analcime by its crystal habit and association.
Leucite identification FAQ
How can you tell if a rock is Leucite?
Check the color (white, gray, colorless, and pale yellow), the vitreous luster, a Mohs hardness of 5.75 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Leucite?
Leucite has a Mohs hardness of 5.75. 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 Leucite and Nepheline?
Leucite (Mohs 5.75, vitreous luster) and Nepheline (Mohs 6, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Leucite vs Nepheline comparison for a side-by-side table.
Is Leucite worth anything?
Entry-level Leucite specimens sell for around $5, typical collector pieces about $35, and premium examples $180 or more depending on size, quality and locality.
What color is Leucite?
Leucite is most often white, gray, colorless, and pale yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
