Identification guide · Organic Gem Materials
How to Identify Jet
Jet is usually black and dark brown with a waxy luster and is opaque. It has a Mohs hardness of 3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Its streak is brown. It is most often confused with Coal, Anthracite, and Shungite; the tests below separate them.
Jet identification checklist
| Color | Black, Dark brown | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Waxy | 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 | 3 | A copper coin (Mohs 3.5) scratches it, but a fingernail does not. |
| Streak | Brown | 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 | 1.3 | Noticeably light in the hand for its size (specific gravity about 1.3). |
| Crystal system | Amorphous |
Jet look-alikes and how to tell them apart
Jet is harder (Mohs 3) than Coal (Mohs 1–2.5), so Jet will scratch Coal and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Jet vs Coal →
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Jet vs Anthracite →
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Jet vs Shungite →
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Is my Jet real?
- Hardness: real Jet sits at Mohs 3. Glass imitations are about 5.5, so use a steel file and a known reference mineral rather than glass alone.
- 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
- Look for an opaque, deep black material that is very light in weight and warm to the touch.
- Jet leaves a brown streak and takes a high, slightly waxy polish without scratching easily.
- Distinguish it from black glass by its warmth and low density, and from coal by its toughness and even texture.
Jet identification FAQ
How can you tell if a rock is Jet?
Check the color (black and dark brown), the waxy luster, a Mohs hardness of 3 and a brown streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Jet?
Jet has a Mohs hardness of 3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Jet and Coal?
Jet (Mohs 3, waxy luster) and Coal (Mohs 1–2.5, dull (lignite) to vitreous (anthracite) luster) look alike, but hardness, streak and heft usually separate them. See the full Jet vs Coal comparison for a side-by-side table.
How do I know if my Jet is real?
Real Jet 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 Jet worth anything?
Entry-level Jet specimens sell for around $5, typical collector pieces about $40, and premium examples $300 or more depending on size, quality and locality.
What color is Jet?
Jet is most often black and dark brown. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
