Franklinphilite
A variety of Stilpnomelane Group
What is Franklinphilite?
Franklinphilite is a phyllosilicate of the stilpnomelane group. Known from only two localities (with a third unconfirmed locality in Switzerland) It was found exclusively from the Franklin and Sterling Hill mines in Franklin, Sussex County, New Jersey. until 2013, when a locality in Wales was confirmed
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Franklinphilite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Franklinphilite Localities Map
See where Franklinphilite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Characteristics of Franklinphilite
Franklinphilite is dark brown to black and possesses a vitreous to slightly resinous luster. It is brittle with a hardness of about 4 (Mohs) and cleaves imperfectly along the {001} plane. The density varies due to impurities, but ranges from 2.6 to 2.8 g/cm compared to the calculated value of 2.66 g/cm. It is translucent to nearly opaque, translucent in thin section and has a light brown streak. Pleochroism is distinctive with X = pale yellow and Y,Z = deep brown. Dispersion was not detected and no evident fluorescence under ultra-violet radiation was observed.
Composition of Franklinphilite
Franklinphilite has an ideal chemical formula of K4(Mn)48(Si,Al)72(O,OH)216·n(H2O) (with n~6). Reported formula is (K,Na)4(Mn2+,Mg,Zn)48(Si,Al)72(O,OH)216·6(H2O).
Quick Facts
Physical Properties
- Color
- Dark brown
- Hardness (Mohs)
- 4
Chemical Properties
- Chemical Formula
- (K,Na)4(Mn2+,Mg,Zn)48(Si,Al)72(O,OH)216 · 6H2O
- Elements
- Al, H, K, Mg, Mn, Na, O, Si, Zn
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Franklinphilite FAQs
How do I identify Franklinphilite?
Franklinphilite can be identified by its hardness of 4 on the Mohs scale, Dark brown color. Look for these key characteristics when examining specimens.
What color is Franklinphilite?
Franklinphilite typically appears in Dark brown. Color can vary depending on impurities and formation conditions.
How hard is Franklinphilite?
Franklinphilite has a hardness of 4 on the Mohs scale. This gives it moderate hardness.
What is the characteristics of franklinphilite of Franklinphilite?
Franklinphilite is dark brown to black and possesses a vitreous to slightly resinous luster. It is brittle with a hardness of about 4 (Mohs) and cleaves imperfectly along the {001} plane. The density varies due to impurities, but ranges from 2.6 to 2.8 g/cm compared to the calculated value of 2.66 g/cm. It is translucent to nearly opaque, translucent in thin section and has a light brown streak. Pleochroism is distinctive with X = pale yellow and Y,Z = deep brown. Dispersion was not detected and no evident fluorescence under ultra-violet radiation was observed.
What is the composition of franklinphilite of Franklinphilite?
Franklinphilite has an ideal chemical formula of K4(Mn)48(Si,Al)72(O,OH)216·n(H2O) (with n~6). Reported formula is (K,Na)4(Mn2+,Mg,Zn)48(Si,Al)72(O,OH)216·6(H2O).