Identification guide · Metamorphic Rocks
How to Identify Phyllite
Phyllite displays a fine-grained, silky to satiny sheen on its foliation surfaces caused by aligned microscopic mica, with colors typically gray, greenish, or silvery, and a hardness around 3 to 4 along the foliation, though harder across it. It splits into sheets along gently wavy or crenulated surfaces rather than the flat planes of slate or the coarse layers of schist. Streak is generally pale and unremarkable. Phyllite sits between slate and schist in grain size and metamorphic grade, and is distinguished from slate primarily by its lustrous sheen, which slate lacks.
Phyllite identification checklist
| Color | Silvery gray, Greenish gray, Black | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Silky to satiny (sericite/chlorite sheen) | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 2.5–4 | A copper coin (Mohs 3.5) scratches it, but a fingernail does not. |
| Fracture | Splintery along foliation, otherwise uneven | |
| Specific gravity | 2.7–2.9 | Ordinary rock-like heft (specific gravity about 2.8), similar to quartz. |
Phyllite look-alikes and how to tell them apart
Greenschist is harder (Mohs 4.5) than Phyllite (Mohs 2.5–4), so Greenschist will scratch Phyllite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Phyllite vs Greenschist →
Schist is harder (Mohs 2.5–7) than Phyllite (Mohs 2.5–4), so Schist will scratch Phyllite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Phyllite vs Schist →
Phyllite is harder (Mohs 2.5–4) than Soapstone (Mohs 1–2.5), so Phyllite will scratch Soapstone and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Phyllite vs Soapstone →
Both sit near Mohs 2.5–4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Phyllite identification FAQ
How can you tell if a rock is Phyllite?
Check the color (silvery gray, greenish gray, and black), the silky to satiny (sericite/chlorite sheen) luster, a Mohs hardness of 2.5–4. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Phyllite?
Phyllite has a Mohs hardness of 2.5–4. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Phyllite and Greenschist?
Phyllite (Mohs 2.5–4, silky to satiny (sericite/chlorite sheen) luster) and Greenschist (Mohs 4.5, silky luster) look alike, but hardness, streak and heft usually separate them. See the full Phyllite vs Greenschist comparison for a side-by-side table.
Is Phyllite worth anything?
Entry-level Phyllite specimens sell for around $1, typical collector pieces about $10, and premium examples $75 or more depending on size, quality and locality.
What color is Phyllite?
Phyllite is most often silvery gray, greenish gray, and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
