Kutnohorite is a manganese-dominant member of the dolomite group that often presents as delicate pinkish, curved rhombohedral crystals. It is most frequently found in hydrothermal vein deposits or manganese ore bodies, often forming as a crust or granular aggregate alongside other manganese minerals.

Hardness

3.5-4

Mohs

Luster

Vitreous to dull

Streak

White

Transparency

Translucent

mineraluncommonDolomite Group family

Kutnohorite

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

Is this kutnohorite?

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 kutnohorite with a known reference. Kutnohorite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to dull.
4
Match the color range
Compare against the expected color range: white, light yellow, light pink.
5
Look at form & habit
Crystal system: trigonal. Typical habit: massive.

Often confused with

Kutnohorite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside kutnohorite

Minerals reported to co-occur with kutnohorite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: CaMn²⁺(CO₃)₂
Mohs hardness: 3.5-4
Density: 3.12 g/cm³
Colors: White Light yellow Light pink
Streak: White
Luster: Vitreous to dull
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Massive
Cleavage: On {1011}, perfect (by analogy to dolomite group)
Rarity: Uncommon
Uses: Collector, Scientific reference
Host rock: Typically in deposits associated with manganiferous sediments

Where rockhounds find kutnohorite

Classic worldwide localities

Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
Sunnyside and Silver King mines, Silverton district, San Juan Co., Colorado, USA
Longvale quarry, Laytonville, Mendocino Co., California, USA
Bald Knob, Alleghany Co., North Carolina, USA
Analyzed material, shown to have the dolomite structure type, occurs at: Kutná Hora and Chvaletice, Czech Republic
Långban, Värmland, Sweden

Field-hunting tip

Where it forms: Typically in deposits associated with manganiferous sediments. If you start seeing rhodochrosite, aragonite, calcite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kutnohorite?+

Mohs hardness is 3.5-4. Luster: vitreous to dull. The streak is white. Common colors include white, light yellow, light pink.

Where is kutnohorite found?+

Notable localities include Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA; Sunnyside and Silver King mines, Silverton district, San Juan Co., Colorado, USA; Longvale quarry, Laytonville, Mendocino Co., California, USA; Bald Knob, Alleghany Co., North Carolina, USA; Analyzed material, shown to have the dolomite structure type, occurs at: Kutná Hora and Chvaletice, Czech Republic.

What rocks look like kutnohorite?+

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

What minerals are found with kutnohorite?+

Kutnohorite commonly co-occurs with Rhodochrosite, Aragonite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kutnohorite form in?+

Where it forms: Typically in deposits associated with manganiferous sediments. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kutnohorite used for?+

Kutnohorite is used in collector, scientific reference.

Find kutnohorite on the map

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