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, 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.