Gageite is a rare manganese silicate typically found as delicate acicular crystals or radial sprays within metamorphosed zinc deposits. It is most famous from the historic mines of the Franklin Mining District in New Jersey, where it is highly prized by mineral collectors for its elegant crystalline habit.
Is this gageite?
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 gageite with a known reference. Gageite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gageite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gageite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, colorless, yellowish-pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous crystals, radial sprays.
Often confused with
Gageite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Manganosite is the harder of the two (Mohs 5-6 vs. 3); streak differs — Gageite leaves white, Manganosite leaves brownish; luster reads vitreous on Gageite and submetallic on Manganosite.
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. 3).
How to tell apart: Hodgkinsonite is the harder of the two (Mohs 4.5-5 vs. 3).
Often found alongside gageite
Minerals reported to co-occur with gageite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn,Mg,Zn)₄₂(Si₆O₁₈)₂(OH)₄₀
- Mohs hardness
- 3
- Density
- 3.66 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or Fibrous Crystals, Radial Sprays
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Zinc Ore Deposits
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find gageite
Classic worldwide localities
- Franklin Mine, New Jersey, USA
- Sterling Hill Mine, New Jersey, USA
Field-hunting tip
Look in metamorphosed zinc ore deposits country — that is the host setting where gageite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a acicular or fibrous crystals, radial sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gageite on the map
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