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 3.75-4.25, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, may be pearly or silky.
- 4Match the color rangeCompare against the expected color range: yellow, brown, gray, white, yellowish brown, yellowish gray, greenish gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal, massive, tabular.
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
- 3.75-4.25
- Density
- 3.96 g/cm³
- Streak
- White
- Luster
- Vitreous, may be pearly or silky
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal, massive, tabular
- Cleavage
- Perfect on {1011}
- Rarity
- Common
- Uses
- Collector, Iron ore
- Host rock
- A common component of bedded sedimentary iron ores and metamorphic iron formations; in hydrothermal metallic veins; rarely in granite and nepheline syenite pegmatites; in carbonatites; authigenic, and in concretions
Where rockhounds find siderite
34 mapped spotsClassic worldwide localities
- Bisbee, Cochise Co., and in the Antler mine, Mohave Co., Arizona, USA
- Leadville, Lake Co., Colorado, USA
- Freiberg and Neudorf, Harz Mountains, and in the Siegerland district, Westphalia, Germany
- Erzberg, near Eisenerz, Styria, and Hüttenberg-Lölling, Carinthia, Austria
- Allevard, Isère, France
- Virtuous Lady mine, Tavistock, Devon, England
Field-hunting tip
Where it forms: A common component of bedded sedimentary iron ores and metamorphic iron formations; in hydrothermal metallic veins; rarely in granite and nepheline syenite pegmatites; in carbonatites; authigenic, and in concretions. If you start seeing quartz, barite, fluorite in float, you are in the right ground. Typical habit: botryoidal, massive, tabular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey, Utah, Illinois. Start trip planning there.
More siderite photos
Common questions
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Find siderite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
