Identification guide · Silicate Minerals
How to Identify Staurolite
Staurolite is usually reddish brown, brown, and dark brown with a vitreous luster and is translucent. It has a Mohs hardness of 7.25. It scratches glass and a steel knife and cannot be scratched by a steel file. Its streak is white to grayish. It is most often confused with Garnet, Quartz, and Moss Agate; the tests below separate them.
Staurolite identification checklist
| Color | Reddish brown, Brown, Dark brown, Black | 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 | 7.25 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Streak | White to grayish | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Distinct in one direction | |
| Fracture | Subconchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.7 | Heavier than it looks (specific gravity about 3.7). |
| Crystal system | Monoclinic |
Extra tests for Staurolite
Glass check. Staurolite 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.
Staurolite look-alikes and how to tell them apart
Both sit near Mohs 7.25, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Staurolite vs Garnet →
Both sit near Mohs 7.25, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Staurolite vs Quartz →
Both sit near Mohs 7.25, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Staurolite vs Moss Agate →
Both sit near Mohs 7.25, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Staurolite vs Rutile →
Field tips
- Look for reddish-brown to dark prismatic crystals, especially distinctive cross-shaped penetration twins.
- High hardness near 7 and occurrence in mica schist with garnet and kyanite are strong clues.
- A dull to vitreous luster and rough crystal surfaces help separate it from glassier minerals.
Staurolite identification FAQ
How can you tell if a rock is Staurolite?
Check the color (reddish brown, brown, dark brown, and black), the vitreous luster, a Mohs hardness of 7.25 and a white to grayish streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Staurolite?
Staurolite has a Mohs hardness of 7.25. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Staurolite and Garnet?
Staurolite (Mohs 7.25, vitreous luster) and Garnet (Mohs 7, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Staurolite vs Garnet comparison for a side-by-side table.
Is Staurolite worth anything?
Entry-level Staurolite specimens sell for around $5, typical collector pieces about $45, and premium examples $300 or more depending on size, quality and locality.
What color is Staurolite?
Staurolite is most often reddish brown, brown, dark brown, and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
