Lennilenapeite
A valid IMA mineral species
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About Lennilenapeite
Flag of the Lenni Lenape of New Jersey
Formula:
K4Mn2+48[Si64Al8]O164(OH)52 · nH2O
The prior (pre-IMA Proposal 25-B) formula was Mg-dominant: K7(Mg,Mn2+,Fe2+,Zn)48(Si,Al)72(O,OH)216 · 16H2O.
Colour:
Very dark in hand sample, chips are dark brown or light green
Lustre:
Vitreous, Resinous
Hardness:
3
Specific Gravity:
2.72
Crystal System:
Triclinic
Member of:
Name:
Named in 1984 by Pete J. Dunn, Donald R. Peacor, and William B. Simmons for the Lenni Lenape indigenous tribe which inhabited the area around Franklin, N.J., USA. The words "Lenni Lenape" mean "the original people" in the Algonquin language of the time.
Type Locality:
Isostructural with:
The formula was changed in 2026 (IMA Proposal 25-B).
Unique Identifiers
Mindat ID:
2375
Long-form identifier:
mindat:1:1:2375:3
IMA Classification of Lennilenapeite
Approved
IMA status notes:
Redefined by the IMA
IMA Formula:
K7(Mg,Mn2+,Fe2+,Zn2+)48(Si,Al)72(O,OH)216·16H2O
Approval year:
1982
First published:
1984
Approval history:
IMA 25-B: Stilpnomelane group: composition range, franklinphilite and ekmanite discredited
lennilenapeite is redefined as a Mn analogue with the end-member formula K4Mn2+ 48[Si64Al8]O164(OH)52·nH2O.
lennilenapeite is redefined as a Mn analogue with the end-member formula K4Mn2+ 48[Si64Al8]O164(OH)52·nH2O.
Classification of Lennilenapeite
9.EG.40
9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings
9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings
74.1.1.2
74 : PHYLLOSILICATES Modulated Layers
1 : Modulated Layers with joined islands
74 : PHYLLOSILICATES Modulated Layers
1 : Modulated Layers with joined islands
16.20.8
16 : Silicates Containing Aluminum and other Metals
20 : Aluminosilicates of Fe, Mg and alkalis
16 : Silicates Containing Aluminum and other Metals
20 : Aluminosilicates of Fe, Mg and alkalis
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Lnl | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Lnl | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Physical Properties of Lennilenapeite
Vitreous, Resinous
Transparency:
Translucent
Colour:
Very dark in hand sample, chips are dark brown or light green
Streak:
Brown
Hardness:
3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Perfect {001} and imperfect nearly perpendicular to (001)
Perfect {001} and imperfect nearly perpendicular to (001)
Density:
2.72 g/cm3 (Measured)
Comment:
Measured using heavy-liquid technique
Optical Data of Lennilenapeite
Type:
Biaxial (-)
RI values:
nα = 1.553(2) nβ = 1.594(4) nγ = 1.594(4)
Max. Birefringence:
δ = 0.041
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
none
Pleochroism:
Strong
Comments:
X faint brown to colorless, Y = Z dark brown (type material)
X pale yellow-brown, Y = Z dark olive brown (cotype material)
X pale yellow-brown, Y = Z dark olive brown (cotype material)
Chemistry of Lennilenapeite
Mindat Formula:
K4Mn2+48[Si64Al8]O164(OH)52 · nH2O
The prior (pre-IMA Proposal 25-B) formula was Mg-dominant: K7(Mg,Mn2+,Fe2+,Zn)48(Si,Al)72(O,OH)216 · 16H2O.
The prior (pre-IMA Proposal 25-B) formula was Mg-dominant: K7(Mg,Mn2+,Fe2+,Zn)48(Si,Al)72(O,OH)216 · 16H2O.
Element Weights:
Common Impurities:
Ca,Ba,Na
Crystallography of Lennilenapeite
Crystal System:
Triclinic
Cell Parameters:
a = 21.9(1) Å
Unit Cell V:
0.00 ų (Calculated from Unit Cell)
Comment:
Point Group: n.d; Space Group: n.d.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 12.11 Å | (100) |
| 2.582 Å | (40) |
| 2.734 Å | (30) |
| 2.365 Å | (30) |
| 1.593 Å | (30) |
| 1.578 Å | (30) |
| 4.07 Å | (20) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Lennilenapeite
General Appearance of Type Material:
Black, lustrous, in small flattened aggregates that range up to 1 cm across.
Place of Conservation of Type Material:
Holotype and cotype lennilenapeite are in the mineral collection at Harvard University, under catalog numbers H105542 and H108573, respectively.
Associated Minerals at Type Locality:
Synonyms of Lennilenapeite
Other Language Names for Lennilenapeite
Relationship of Lennilenapeite to other Species
Member of:
Other Members of Stilpnomelane Group:
| Parsettensite | (K,Na,Ca)7.5(Mn,Mg)49Si72O168(OH)50 · nH2O | Mon. 2/m : B2/m |
| Stilpnomelane | K4Fe2+48[Si64Al8]O164(OH)52 · nH2O | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
| 25 photos of Lennilenapeite associated with Sphalerite | ZnS |
| 19 photos of Lennilenapeite associated with Calcite | CaCO3 |
| 17 photos of Lennilenapeite associated with Franklinite | Zn2+Fe3+2O4 |
| 10 photos of Lennilenapeite associated with Willemite | Zn2SiO4 |
| 7 photos of Lennilenapeite associated with Baryte | BaSO4 |
| 7 photos of Lennilenapeite associated with Hematite | Fe2O3 |
| 7 photos of Lennilenapeite associated with Hodgkinsonite | Mn2+Zn2(SiO4)(OH)2 |
| 2 photos of Lennilenapeite associated with Quartz | SiO2 |
| 1 photo of Lennilenapeite associated with Dolomite | CaMg(CO3)2 |
| 1 photo of Lennilenapeite associated with Rhodonite | CaMn3Mn[Si5O15] |
Related Minerals - Strunz-mindat Grouping
| 9.EG.05 | Cymrite | BaAl2Si2(O,OH)8 · H2O |
| 9.EG.10 | Naujakasite | (Na,K)6(Fe2+,Mn2+,Ca)(Al,Fe)4Si8O26 |
| 9.EG.10 | Manganonaujakasite | Na6(Mn2+,Fe2+)Al4Si8O26 |
| 9.EG.15 | Dmisteinbergite | Ca(Al2Si2O8) |
| 9.EG.20 | Kampfite | Ba12(Si11Al5)O31(CO3)8Cl5 |
| 9.EG.25 | Vertumnite | Ca4Al4Si4O6(OH)24 · 3H2O |
| 9.EG.25 | Strätlingite | Ca2Al2SiO7 · 8H2O |
| 9.EG.30 | Eggletonite | (Na,K,Ca)xMn6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.30 | Ganophyllite | (K,Na)xMn2+6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.30 | Tamaite | (Ca,K,Na)xMn6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.35 | Zussmanite | K(Fe,Mg,Mn)13(Si,Al)18O42(OH)14 |
| 9.EG.35 | Coombsite | KMn2+13(Si,Al)18O42(OH)14 |
| 9.EG.40 | 'Chalcodite' | K(Fe3+,Mg,Fe2+)8(Si,Al)12(O,OH)27 |
| 9.EG.40 | Parsettensite | (K,Na,Ca)7.5(Mn,Mg)49Si72O168(OH)50 · nH2O |
| 9.EG.40 | Stilpnomelane | K4Fe2+48[Si64Al8]O164(OH)52 · nH2O |
| 9.EG.45 | Latiumite | (Ca,K)4(Si,Al)5O11(SO4,CO3) |
| 9.EG.45 | Levantite | KCa3Al2(SiO4)(Si2O7)(PO4) |
| 9.EG.45 | Tuscanite | KCa6(Si,Al)10O22(SO4,CO3)2(OH) · H2O |
| 9.EG.50 | Jagoite | Pb18Fe3+4[Si4(Si,Fe3+)6][Pb4Si16(Si,Fe)4]O82Cl6 |
| 9.EG.50 | Friisite | Pb8Al3Si8O27Cl3 |
| 9.EG.55 | Wickenburgite | CaPb3Al2Si10O24(OH)6 |
| 9.EG.60 | Hyttsjöite | Pb18Ba2Ca5Mn2+2Fe3+2Si30O90Cl · 6H2O |
| 9.EG.65 | Armbrusterite | K5Na7Mn15[(Si9O22)4](OH)10 · 4H2O |
| 9.EG.70 | Roymillerite | Pb24Mg9(Si10O28)(CO3)10(BO3)(SiO4)(OH)13O5 |
| 9.EG.70 | Britvinite | [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)] |
| 9.EG.75 | Kayupovaite | Na2Mn10[(Si14Al2)O38(OH)8] · 7H2O |
| 9.EG.75 | 'UM1989-30-SiO:AlBaCaFeHKMgMn' | (Ba,Ca)(Mn,Fe,Mg)22(Si,Al)32O76(OH)16 · 12H2O |
| 9.EG.75 | Bannisterite | (Ca,K,Na)(Mn2+,Fe2+)10(Si,Al)16O38(OH)8 · nH2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 1.8768% | 582 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Lennilenapeite
No discernible fluorescence in ultraviolet radiation
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Lennilenapeite
mindat.org URL:
https://www.mindat.org/min-2375.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
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References for Lennilenapeite
Reference List:
Dunn, Pete J., Peacor, Donald R., Simmons, William B. (1984) Lennilenapeite, the Mg-analogue of stilpnomelane, and chemical data on other stilpnomelane species from Franklin, New Jersey. The Canadian Mineralogist, 22 (2) 259-263
Localities for Lennilenapeite
Showing 7 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Japan | |
| Endo (2008) |
Romania | |
| minerals-of-the-carpathians.eu (2008) |
| Hîrtopanu (1997) +1 other reference |
UK | |
| Cotterell et al. (2013) |
USA | |
| Färber (n.d.) |
| Dunn et al. (1984) +1 other reference |
| King |
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Franklin Mine, Franklin, Sussex County, New Jersey, USA