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.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralcommonCalcite Group family

Siderite

Also: chalybite, spathic iron

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this siderite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try 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.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Siderite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Siderite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brown, gray, white.
5
Look at form & habit
Crystal 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
Colors: Yellow Brown Gray White
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

33 mapped spots

Classic 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, 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, Illinois. Start trip planning there.

Browse 33 U.S. spots for siderite →

Common questions

How do you identify siderite?+

Mohs hardness is 3.5-4. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brown, gray, white.

Where is siderite found?+

Notable localities include Allevard, France; Panasqueira, Portugal; Cornwall, England; Mont Saint-Hilaire, Canada; Boulder County, Colorado, USA.

Can I find siderite in the United States?+

RockHoundR maps 33 siderite rockhounding spots across 12 U.S. states. The top states are New Jersey, Utah, Illinois.

How much is siderite worth?+

Typical asking prices fall in the range of $10-100 thumbnail, $50-500 cabinet specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like siderite?+

Siderite is most often confused with Dolomite, Ankerite, Calcite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with siderite?+

Siderite commonly co-occurs with Pyrite, Quartz, Fluorite, Galena, Sphalerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does siderite form in?+

Siderite typically forms in hydrothermal veins, sedimentary rocks, iron-rich metamorphic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is siderite used for?+

Siderite is used in collector, iron ore.

Find siderite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.