Franklinphilite is a rare phyllosilicate mineral of the stilbite group, found almost exclusively in the famous zinc deposits of Franklin and Sterling Hill, New Jersey. Collectors should look for thin, platy crystals occurring as radiating clusters within metamorphosed zinc ores, often associated with willemite and franklinite.
Is this franklinphilite?
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 franklinphilite with a known reference. Franklinphilite 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: light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to slightly resinous.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy, radial.
Often confused with
Franklinphilite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside franklinphilite
Minerals reported to co-occur with franklinphilite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na,Ca)₃Mn₃Si₁₈O₄₄·12H₂O
- Mohs hardness
- 4
- Density
- 2.6-2.8 g/cm³
- Colors
- Streak
- Light brown
- Luster
- Vitreous to slightly resinous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy, radial
- Cleavage
- Imperfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a veinlet crosscutting a breccia of calcite, aegirine, and serpentine in a metamorphosed stratiform zinc deposit
Where rockhounds find franklinphilite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: In a veinlet crosscutting a breccia of calcite, aegirine, and serpentine in a metamorphosed stratiform zinc deposit. If you start seeing friedelite, nelenite, rhodonite in float, you are in the right ground. Typical habit: platy, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify franklinphilite?+
Where is franklinphilite found?+
What rocks look like franklinphilite?+
What minerals are found with franklinphilite?+
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What is franklinphilite used for?+
Find franklinphilite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
