Bostwickite is a rare manganese silicate mineral primarily found in the ore bodies of the Franklin Mining District in New Jersey. It is highly valued by collectors for its striking bright orange fluorescence under short-wave ultraviolet light and its distinctive fibrous, acicular crystal habit.
Is this bostwickite?
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 bostwickite with a known reference. Bostwickite sits at Mohs ~1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish red.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to submetallic on prism surfaces.
- 4Match the color rangeCompare against the expected color range: dark red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: divergent, prismatic.
Often confused with
Bostwickite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside bostwickite
Minerals reported to co-occur with bostwickite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMn₆Si₃O₁₆·7H₂O
- Mohs hardness
- ~1
- Density
- 2.93 g/cm³
- Colors
- Streak
- Brownish red
- Luster
- Vitreous to submetallic on prism surfaces
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Divergent, prismatic
- Cleavage
- None
- Fluorescence
- Bright orange under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a metamorphosed stratiform zinc deposit, on surfaces of ore and on secondary carbonate minerals
Where rockhounds find bostwickite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: In a metamorphosed stratiform zinc deposit, on surfaces of ore and on secondary carbonate minerals. If you start seeing franklinite, calcite, fluorite in float, you are in the right ground. Typical habit: divergent, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bostwickite?+
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What rocks look like bostwickite?+
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Find bostwickite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
