Identification guide · Igneous Rocks
How to Identify Trachyte
Trachyte is usually light gray, tan, and pink with a dull luster and is opaque. 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 light gray to white. It is most often confused with Ignimbrite, Monzonite, and Tonalite; the tests below separate them.
Trachyte identification checklist
| Color | Light gray, Tan, Pink, Brown, Greenish gray, White | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Dull | 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 | 6 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Light gray to white | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None to variable by phenocrysts | |
| Fracture | Uneven to conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.6 | Ordinary rock-like heft (specific gravity about 2.6), similar to quartz. |
Trachyte 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. Trachyte vs Ignimbrite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Trachyte vs Monzonite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Trachyte vs Tonalite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for light gray, tan, pinkish, or brown fine-grained volcanic texture.
- Feldspar phenocrysts can support trachyte when visible.
- Trachyte generally looks lighter and more feldspar-rich than basalt.
- It can overlap visually with rhyolite or andesite, so context helps.
Trachyte identification FAQ
How can you tell if a rock is Trachyte?
Check the color (light gray, tan, pink, and brown), the dull luster, a Mohs hardness of 6 and a light gray to white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Trachyte?
Trachyte 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 Trachyte and Ignimbrite?
Trachyte (Mohs 6, dull luster) and Ignimbrite (Mohs 6, dull luster) look alike, but hardness, streak and heft usually separate them. See the full Trachyte vs Ignimbrite comparison for a side-by-side table.
Is Trachyte worth anything?
Entry-level Trachyte 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 Trachyte?
Trachyte is most often light gray, tan, pink, and brown. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
