Identification guide · Organic Gems
How to Identify Red Coral
Red Coral is usually red, pink, and orange with a vitreous luster and is opaque. It has a Mohs hardness of 3.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Its streak is white. It is most often confused with Calcite, Aragonite, and Rhodochrosite; the tests below separate them.
Red Coral identification checklist
| Color | Red, Pink, Orange, White | 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 | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 3.5 | A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None | |
| Fracture | Uneven | |
| Specific gravity | 2.65 | Ordinary rock-like heft (specific gravity about 2.65), similar to quartz. |
| Crystal system | Trigonal |
Extra tests for Red Coral
Acid test. Fizzes in vinegar or dilute hydrochloric acid because of its carbonate content.
Red Coral look-alikes and how to tell them apart
Both sit near Mohs 3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Red Coral vs Calcite →
Both sit near Mohs 3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Red Coral vs Aragonite →
Both sit near Mohs 3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Red Coral vs Rhodochrosite →
Both sit near Mohs 3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Red Coral vs Pearl →
Is my Red Coral real?
- Hardness: real Red Coral sits at Mohs 3.5. 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
- Check whether the specimen's color and texture match typical Red Coral examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Red Coral identification FAQ
How can you tell if a rock is Red Coral?
Check the color (red, pink, orange, and white), the vitreous luster, a Mohs hardness of 3.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Red Coral?
Red Coral has a Mohs hardness of 3.5. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
What is the difference between Red Coral and Calcite?
Red Coral (Mohs 3.5, vitreous luster) and Calcite (Mohs 3, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Red Coral vs Calcite comparison for a side-by-side table.
How do I know if my Red Coral is real?
Real Red Coral 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 Red Coral worth anything?
Entry-level Red Coral specimens sell for around $50, typical collector pieces about $300, and premium examples $3000 or more depending on size, quality and locality.
What color is Red Coral?
Red Coral is most often red, pink, orange, and white. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
