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 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellowish red, dark red, pink, orange.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, massive, tabular.
Often confused with
Holdenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Holdenite leaves white, Sphalerite leaves pale brown to pale yellow and white; luster reads vitreous on Holdenite and resinous to adamantine on Sphalerite.
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. 4).
How to tell apart: Streak differs, so Holdenite leaves white, Zincite leaves yellow-orange; luster reads vitreous on Holdenite and subadamantine to resinous 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
- Mn₆Zn₃(AsO₄)₂(SiO₄)(OH)₈
- Mohs hardness
- 4
- Density
- 4.11 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, massive, tabular
- Cleavage
- {010}, poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in veinlets, on slip surfaces, and as interstitial fillings within a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA)
Where rockhounds find holdenite
Classic worldwide localities
- Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: A secondary mineral in veinlets, on slip surfaces, and as interstitial fillings within a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA). If you start seeing franklinite, willemite, pyrochroite in float, you are in the right ground. Typical habit: aggregates, massive, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify holdenite?+
Where is holdenite found?+
Is holdenite safe to handle?+
What rocks look like holdenite?+
What minerals are found with holdenite?+
What kind of rock does holdenite form in?+
What is holdenite used for?+
Find holdenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
