Identification guide · Quartz Family
How to Identify Smoky Quartz
Smoky Quartz is usually brown, gray, and black with a vitreous luster and is transparent. It has a Mohs hardness of 7. It scratches glass and a steel knife and cannot be scratched by a steel file. Its streak is white. It is most often confused with Quartz, Clear Quartz, and Dendritic Agate; the tests below separate them.
Smoky Quartz identification checklist
| Color | Brown, Gray, 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 | Transparent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 7 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.65 | Ordinary rock-like heft (specific gravity about 2.65), similar to quartz. |
| Crystal system | Hexagonal |
Extra tests for Smoky Quartz
Glass check. Smoky Quartz 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.
Smoky Quartz look-alikes and how to tell them apart
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Smoky Quartz vs Quartz →
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Smoky Quartz vs Clear Quartz →
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Smoky Quartz vs Dendritic Agate →
Smoky Quartz is harder (Mohs 7) than Andesite (Mohs 5–6), so Smoky Quartz will scratch Andesite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
Is my Smoky Quartz real?
- Hardness: real Smoky Quartz sits at Mohs 7. Glass imitations are about 5.5, so genuine Smoky Quartz scratches glass while a glass fake cannot.
- Bubbles: round gas bubbles under a 10x loupe mean glass or resin, never a natural stone.
- Color: dyed material concentrates color in cracks and pores; look for pigment collecting at the edges of fractures.
- Temperature: natural crystals feel cool and take longer to warm in your hand than plastic or resin.
Field tips
- Check whether the specimen's color and texture match typical Smoky Quartz examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Smoky Quartz identification FAQ
How can you tell if a rock is Smoky Quartz?
Check the color (brown, gray, and black), the vitreous luster, a Mohs hardness of 7 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Smoky Quartz?
Smoky Quartz has a Mohs hardness of 7. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Smoky Quartz and Quartz?
Smoky Quartz (Mohs 7, vitreous luster) and Quartz (Mohs 7, vitreous, greasy on fracture surfaces luster) look alike, but hardness, streak and heft usually separate them. See the full Smoky Quartz vs Quartz comparison for a side-by-side table.
How do I know if my Smoky Quartz is real?
Real Smoky Quartz matches the hardness listed above, shows no round gas bubbles under magnification, and does not concentrate dye in cracks. Glass and resin fakes fail at least one of those checks.
Is Smoky Quartz worth anything?
Entry-level Smoky Quartz 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 Smoky Quartz?
Smoky Quartz is most often brown, gray, and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
