Siderite is an iron carbonate mineral often recognized by its curved rhombohedral crystal faces and characteristic brownish color. Collectors look for sharp, well-defined crystals associated with metallic sulfides in hydrothermal veins. It frequently tarnishes to darker shades of brown or black upon exposure to air.
Is this siderite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch siderite with a known reference. Siderite sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Siderite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Siderite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, gray, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals, botryoidal, massive.
Often confused with
Siderite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside siderite
Minerals reported to co-occur with siderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeCO₃
- Mohs hardness
- 3.5-4
- Density
- 3.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral Crystals, Botryoidal, Massive
- Cleavage
- Perfect Rhombohedral
- Rarity
- Common
- Uses
- Collector, Iron Ore
- Host rock
- Hydrothermal Veins, Sedimentary Rocks, Iron-rich Metamorphic Deposits
- Typical price
- $10-100 thumbnail, $50-500 cabinet specimen
Where rockhounds find siderite
32 mapped spotsClassic worldwide localities
- Allevard, France
- Panasqueira, Portugal
- Cornwall, England
- Mont Saint-Hilaire, Canada
- Boulder County, Colorado, USA
Field-hunting tip
Look in hydrothermal veins, sedimentary rocks, iron-rich metamorphic deposits country — that is the host setting where siderite typically forms. If you start seeing pyrite, quartz, fluorite in float, you are in the right ground. Field specimens usually show a rhombohedral crystals, botryoidal, massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey, Utah, Indiana — start trip planning there.
Common questions
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Find siderite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
