Galaxite is a rare member of the spinel group, typically found as opaque, black, octahedral crystals. It is most famous for its occurrence in the manganese-rich deposits of Bald Knob, where it often forms alongside other manganese-bearing minerals.
Is this galaxite?
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 galaxite with a known reference. Galaxite sits at Mohs 7.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Galaxite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Galaxite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, reddish-brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals, massive, granular.
Often confused with
Galaxite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Galaxite is noticeably harder (Mohs 7.5 vs. 5.5-6.5); luster reads submetallic on Galaxite and metallic on Magnetite.
How to tell apart: Galaxite is noticeably harder (Mohs 7.5 vs. 5.5); streak differs, so Galaxite leaves black, Chromite leaves dark brown.
How to tell apart: Galaxite is noticeably harder (Mohs 7.5 vs. 5.5-6.5); streak differs, so Galaxite leaves black, Franklinite leaves reddish-brown; luster reads submetallic on Galaxite and metallic on Franklinite.
Often found alongside galaxite
Minerals reported to co-occur with galaxite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnAl₂O₄
- Mohs hardness
- 7.5
- Density
- 4.2-4.5 g/cm³
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Manganese Deposits
- Typical price
- $20-150 for small specimens
Where rockhounds find galaxite
Classic worldwide localities
- Bald Knob, North Carolina, USA
- Långban, Sweden
- Jacupiranga, Brazil
Field-hunting tip
Look in metamorphosed manganese deposits country, the host setting where galaxite typically forms. If you start seeing spessartine, rhodonite, tephroite in float, you are in the right ground. Field specimens usually show a octahedral crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find galaxite on the map
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