Calderite is a rare manganese-iron garnet species primarily found in manganese-rich metamorphic environments. It is notoriously difficult to distinguish visually from other garnets like Spessartine without chemical analysis, though its association with black manganese ores is a helpful diagnostic clue for collectors.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrareGarnet Group family

Calderite

Hardness: 7
Luster: Vitreous
Streak: White
Transparency: Semitransparent

Is this calderite?

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 calderite with a known reference. Calderite sits at Mohs 7, 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.
4
Match the color range
Compare against the expected color range: dark yellow, reddish yellow.
5
Look at form & habit
Crystal system: cubic. Typical habit: dodecahedral crystals, massive, granular.

Often confused with

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

How to tell apart: Luster reads vitreous on Calderite and adamantine to resinous, dull on Andradite.

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Often found alongside calderite

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

All properties

Chemical formula: Mn₃Fe₂(SiO₄)₃
Mohs hardness: 7
Density: 4.05 g/cm³
Colors: Dark yellowReddish yellow
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Cubic
Crystal habit: Dodecahedral crystals, massive, granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a manganese deposit (Otjosondu, Namibia); in an iron formation (Wabush district, Canada)

Where rockhounds find calderite

Classic worldwide localities

Katkamsandi, Hazaribagh district, Bihar, and at Netra, Balaghat district, Madhya Pradesh, India
Otjosondu, Namibia
Wabush district, near Labrador City, Labrador, Newfoundland, Canada
Fianel mine, Val Ferrera, Graubünden, Switzerland

Field-hunting tip

Where it forms: In a manganese deposit (Otjosondu, Namibia); in an iron formation (Wabush district, Canada). If you start seeing pyrolusite, aegirine, rhodonite in float, you are in the right ground. Typical habit: dodecahedral crystals, massive, granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify calderite?+

Mohs hardness is 7. Luster: vitreous. The streak is white. Common colors include dark yellow, reddish yellow.

Where is calderite found?+

Notable localities include Katkamsandi, Hazaribagh district, Bihar, and at Netra, Balaghat district, Madhya Pradesh, India; Otjosondu, Namibia; Wabush district, near Labrador City, Labrador, Newfoundland, Canada; Fianel mine, Val Ferrera, Graubünden, Switzerland.

What rocks look like calderite?+

Calderite is most often confused with Spessartine, Andradite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with calderite?+

Calderite commonly co-occurs with Pyrolusite, Aegirine, Rhodonite, Hematite, Rhodochrosite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does calderite form in?+

Where it forms: In a manganese deposit (Otjosondu, Namibia); in an iron formation (Wabush district, Canada). Working float back to the host body is the standard way to chase a fresh occurrence.

What is calderite used for?+

Calderite is used in collector.

Find calderite on the map

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