RocksdayErythrite vs Rhodochrosite
How to tell them apart
A crimson-pink cobalt arsenate that forms where cobalt ores weather.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A manganese carbonate in raspberry-red crystals or rose-and-white banded stalactites.
Photo: JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0
Quick tests
- Fingernail: A fingernail scratches Erythrite (Mohs 1.5–2.5) but not Rhodochrosite (Mohs 3.5–4).
- Acid (vinegar or dilute HCl): Rhodochrosite fizzes weakly, or only when powdered or warmed; Erythrite doesn't.
- Streak (rub on unglazed porcelain): Erythrite leaves a pale pink streak; Rhodochrosite leaves white.
Key differences
- Rhodochrosite is harder and fizzes in warm acid.
Side by side
| Property | Erythrite | Rhodochrosite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 1.5–2.5 | 3.5–4 |
| Luster | Adamantine to pearly | Vitreous |
| Streak | Pale pink | White |
| Colors | Pink, Purple, Red | Pink, Red |
| Crystal system | Monoclinic | Trigonal |
| Specific gravity | 3.06 | 3.5–3.7 |
| Formula | Co₃(AsO₄)₂·8H₂O | MnCO₃ |
| Found in | Bou Azzer, Morocco; Cobalt, Ontario | Capillitas, Argentina; Sweet Home Mine, Colorado |
Properties that are the same for both are grayed out.
How to identify erythrite
- Crimson to pink crusts or radiating crystals.
- Very soft.
- Often coats dark cobalt ores.
Crystal system: Monoclinic
Full Erythrite guide →How to identify rhodochrosite
- Rose-pink to red, often banded.
- Rhomb-shaped crystals and cleavage.
- Fizzes in warm acid.
- Soft — a knife scratches it.
Crystal system: Trigonal
Full Rhodochrosite guide →More comparisons
Could you tell them apart from a blurry close-up?
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