Freudenbergite is a rare sodium iron titanate mineral found primarily in alkaline igneous environments. It typically appears as small, dark brown to black tabular crystals and is prized by advanced mineral collectors for its scarcity and unique chemical composition.
Is this freudenbergite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch freudenbergite with a known reference. Freudenbergite sits at Mohs <5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brownish black, gray, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular.
Often confused with
Freudenbergite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Freudenbergite leaves pale yellow-brown, Ilmenite leaves black to reddish brown; luster reads vitreous on Freudenbergite and metallic to submetallic on Ilmenite.
How to tell apart: Streak differs, so Freudenbergite leaves pale yellow-brown, Hematite leaves cherry-red or reddish brown; luster reads vitreous on Freudenbergite and metallic or submetallic to dull on Hematite.
Often found alongside freudenbergite
Minerals reported to co-occur with freudenbergite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na(Ti₃Fe)O₈
- Mohs hardness
- <5
- Density
- 3.956 g/cm³
- Colors
- Streak
- Pale yellow-brown
- Luster
- Vitreous
- Transparency
- Opaque, transparent in thin fragments
- Crystal system
- Monoclinic
- Crystal habit
- Granular
- Cleavage
- {001}, and another prismatic, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral in an apatite-bearing alkali syenite
Where rockhounds find freudenbergite
Classic worldwide localities
- Found at Michelsberg, on the Katzenbuckel, Odenwald, Baden-Württemberg, Germany
Field-hunting tip
Where it forms: A late-stage mineral in an apatite-bearing alkali syenite. If you start seeing hematite, högbomite, diopside in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find freudenbergite on the map
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