Ogdensburgite is a rare secondary arsenic-bearing mineral discovered at the famous Franklin-Sterling Hill mining district. It typically appears as delicate, bright yellow acicular or lath-like crystals forming small sprays or crusts on ore specimens.
Is this ogdensburgite?
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 ogdensburgite with a known reference. Ogdensburgite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale orange.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous on cleavages.
- 4Match the color rangeCompare against the expected color range: brownish red, dark brown, reddish orange.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: bladed, encrustations, micaceous.
Often confused with
Ogdensburgite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Veszelyite is the harder of the two (Mohs 3.5-4 vs. ~2); streak differs, so Ogdensburgite leaves pale orange, Veszelyite leaves green to white; luster reads resinous on cleavages on Ogdensburgite and vitreous on Veszelyite.
How to tell apart: Austinite is the harder of the two (Mohs 4-4.5 vs. ~2); streak differs, so Ogdensburgite leaves pale orange, Austinite leaves white; luster reads resinous on cleavages on Ogdensburgite and subadamantine to silky in aggregates on Austinite.
Often found alongside ogdensburgite
Minerals reported to co-occur with ogdensburgite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Fe₄Zn(AsO₄)₄(OH)₆·6H₂O
- Mohs hardness
- ~2
- Density
- 3.11 g/cm³
- Streak
- Pale orange
- Luster
- Resinous on cleavages
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Bladed, encrustations, micaceous
- Cleavage
- On {001}, perfect; on {010}, {100}, poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- On oxidized ore from a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA); in oxidized ore from an arsenic-rich polymetallic hydrothermal ore deposit (Ojuela mine, Mexico)
Where rockhounds find ogdensburgite
Classic worldwide localities
- Sterling Hill, Ogdensburg, New Jersey, USA
- Ojuela mine, Mapimí, Durango, Mexico
- Clara mine, near Oberwolfach, Black Forest, Germany
Field-hunting tip
Where it forms: On oxidized ore from a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA); in oxidized ore from an arsenic-rich polymetallic hydrothermal ore deposit (Ojuela mine, Mexico). If you start seeing parasymplesite, köttigite, yukonite in float, you are in the right ground. Typical habit: bladed, encrustations, micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
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Find ogdensburgite on the map
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