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

7-7.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareGarnet Group family

Calderite

Hardness: 7-7.5
Luster: Vitreous
Streak: White
Transparency: Translucent

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 7-7.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Calderite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Calderite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: reddish-brown, brown, orange-brown.
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.

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: Mn³⁺₂Fe³⁺₂(SiO₄)₃
Mohs hardness: 7-7.5
Density: 3.9-4.0 g/cm³
Colors: Reddish-brown Brown Orange-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Cubic
Crystal habit: Dodecahedral Crystals, Massive, Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Manganese Deposits
Typical price: $50-500 depending on specimen quality and size

Where rockhounds find calderite

Classic worldwide localities

Kodur, India
Jakobsberg, Sweden
Franklin, New Jersey, USA
Otanmäki, Finland

Field-hunting tip

Look in metamorphosed manganese deposits country — that is the host setting where calderite typically forms. If you start seeing braunite, hausmannite, bixbyite in float, you are in the right ground. Field specimens usually show a dodecahedral crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify calderite?+

Mohs hardness is 7-7.5. It typically shows a vitreous luster. The streak is white. Common colors include reddish-brown, brown, orange-brown.

Where is calderite found?+

Notable localities include Kodur, India; Jakobsberg, Sweden; Franklin, New Jersey, USA; Otanmäki, Finland.

How much is calderite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen quality and size. Quality, size, and provenance can move individual specimens well outside that range.

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 Braunite, Hausmannite, Bixbyite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does calderite form in?+

Calderite typically forms in metamorphosed manganese deposits. 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.