Holdenite is a rare arsenate mineral most famously found in the Franklin and Sterling Hill mining districts. It is highly prized by collectors for its vibrant red-to-pink coloration and its brilliant yellow fluorescence under shortwave ultraviolet light.
Is this holdenite?
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 holdenite with a known reference. Holdenite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Holdenite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Holdenite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: red, pink, orange-red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, massive, granular.
Often confused with
Holdenite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Holdenite leaves white, Sphalerite leaves white to yellow-brown; luster reads vitreous on Holdenite and resinous to submetallic on Sphalerite.
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. 3-4).
How to tell apart: Streak differs — Holdenite leaves white, Zincite leaves orange-yellow; luster reads vitreous on Holdenite and sub-adamantine on Zincite.
Often found alongside holdenite
Minerals reported to co-occur with holdenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn,Zn,Mg)₈(Zn,Mg)(AsO₄)₂(OH)₈
- Mohs hardness
- 3-4
- Density
- 4.15 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Massive, Granular
- Cleavage
- Poor On {110}
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Metamorphic Zinc Ore Bodies
- Typical price
- $50-500 thumbnail, $500-2000 cabinet specimen
Where rockhounds find holdenite
Classic worldwide localities
- Franklin, New Jersey, USA
- Sterling Hill, New Jersey, USA
Field-hunting tip
Look in hydrothermal metamorphic zinc ore bodies country — that is the host setting where holdenite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find holdenite on the map
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