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Llyn du Bach mine, Llanfair, Gwynedd, Wales, UKi
Regional Level Types
Llyn du Bach mineMine (Abandoned)
LlanfairCommunity
GwyneddCounty
WalesCountry
UKCountry

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PhotosMapsSearchMineralogy
00176780017820616722449.jpg
Lennilenapeite, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
00628970017913811759207.jpg
Spessartine, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
07032960017272327293871.jpg
Caryopilite, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
09061810017820611026561.jpg
Lennilenapeite, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
05699140017913187904463.jpg
Spessartine, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
07032960017272327293871.jpg
Caryopilite, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
00176780017820616722449.jpg
Lennilenapeite, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
07540530017916449008357.jpg
Spessartine, etc.

Llyn du Bach mine, Llanfair, Gwynedd, Wales, UK
Latitude & Longitude (WGS84):
52° 53' 14'' North , 3° 59' 43'' West
Latitude & Longitude (decimal):
52.88742,-3.99546
GRN:
N36W02
UK National Grid Reference:
SH657323
Type:
Mine (Abandoned) - last checked 2026
Köppen climate type:
Cfb : Temperate oceanic climate
Nearest Settlements:
PlacePopulationDistance
Trawsfynydd628 (2017)5.1km
Penrhyndeudraeth1,546 (2017)7.0km
Harlech1,762 (2017)8.2km
Llan Ffestiniog864 (2017)8.9km
Porthmadog2,981 (2017)10.2km
Mindat Locality ID:
254997
Long-form identifier:
mindat:1:2:254997:5
GUID (UUID V4):
0
Other/historical names associated with this locality:
Merionethshire


Disused manganese mine north-east of Llyn du Bach, first UK record of "franklinphilite" (= lennilenapeite).

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


10 valid minerals. 1 erroneous literature entry.

Detailed Mineral List:

ⓘ Alleghanyite
Formula: Mn2+5(SiO4)2(OH)2
ⓘ Caryopilite
Formula: Mn2+3Si2O5(OH)4
ⓘ 'Franklinphilite'
Description: = lennilenapeite (IMA Proposal 25-B (2026)).
ⓘ Jacobsite ?
Formula: Mn2+Fe3+2O4
ⓘ Kellyite
Formula: Mn2+2Al(AlSiO5)(OH)4
ⓘ Lennilenapeite
Formula: K4Mn2+48[Si64Al8]O164(OH)52 · nH2O
ⓘ Quartz
Formula: SiO2
ⓘ Rhodochrosite
Formula: MnCO3
ⓘ Sonolite
Formula: Mn2+9(SiO4)4(OH)2
ⓘ Spessartine
Formula: Mn2+3Al2(SiO4)3
ⓘ Tephroite
Formula: Mn2+2(SiO4)

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
ⓘJacobsite ?4.BB.05Mn2+Fe3+2O4
ⓘQuartz4.DA.05SiO2
Group 5 - Nitrates and Carbonates
ⓘRhodochrosite5.AB.05MnCO3
Group 9 - Silicates
ⓘ'Franklinphilite' ?9..
ⓘTephroite9.AC.05Mn2+2(SiO4)
ⓘSpessartine9.AD.25Mn2+3Al2(SiO4)3
ⓘAlleghanyite9.AF.45Mn2+5(SiO4)2(OH)2
ⓘSonolite9.AF.55Mn2+9(SiO4)4(OH)2
ⓘCaryopilite9.ED.15Mn2+3Si2O5(OH)4
ⓘKellyite9.ED.15Mn2+2Al(AlSiO5)(OH)4
ⓘLennilenapeite9.EG.40K4Mn2+48[Si64Al8]O164(OH)52 · nH2O

List of minerals for each chemical element

HHydrogen
Hⓘ AlleghanyiteMn52+(SiO4)2(OH)2
Hⓘ CaryopiliteMn32+Si2O5(OH)4
Hⓘ KellyiteMn22+Al(AlSiO5)(OH)4
Hⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
Hⓘ SonoliteMn92+(SiO4)4(OH)2
CCarbon
Cⓘ RhodochrositeMnCO3
OOxygen
Oⓘ AlleghanyiteMn52+(SiO4)2(OH)2
Oⓘ CaryopiliteMn32+Si2O5(OH)4
Oⓘ JacobsiteMn2+Fe23+O4
Oⓘ KellyiteMn22+Al(AlSiO5)(OH)4
Oⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
Oⓘ QuartzSiO2
Oⓘ RhodochrositeMnCO3
Oⓘ SonoliteMn92+(SiO4)4(OH)2
Oⓘ SpessartineMn32+Al2(SiO4)3
Oⓘ TephroiteMn22+(SiO4)
AlAluminium
Alⓘ KellyiteMn22+Al(AlSiO5)(OH)4
Alⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
Alⓘ SpessartineMn32+Al2(SiO4)3
SiSilicon
Siⓘ AlleghanyiteMn52+(SiO4)2(OH)2
Siⓘ CaryopiliteMn32+Si2O5(OH)4
Siⓘ KellyiteMn22+Al(AlSiO5)(OH)4
Siⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
Siⓘ QuartzSiO2
Siⓘ SonoliteMn92+(SiO4)4(OH)2
Siⓘ SpessartineMn32+Al2(SiO4)3
Siⓘ TephroiteMn22+(SiO4)
KPotassium
Kⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
MnManganese
Mnⓘ AlleghanyiteMn52+(SiO4)2(OH)2
Mnⓘ CaryopiliteMn32+Si2O5(OH)4
Mnⓘ JacobsiteMn2+Fe23+O4
Mnⓘ KellyiteMn22+Al(AlSiO5)(OH)4
Mnⓘ LennilenapeiteK4Mn482+[Si64Al8]O164(OH)52 · nH2O
Mnⓘ RhodochrositeMnCO3
Mnⓘ SonoliteMn92+(SiO4)4(OH)2
Mnⓘ SpessartineMn32+Al2(SiO4)3
Mnⓘ TephroiteMn22+(SiO4)
FeIron
Feⓘ JacobsiteMn2+Fe23+O4

Other Regions, Features and Areas containing this locality

British and Irish IslesGroup of Islands
Eurasian PlateTectonic Plate
EuropeContinent
UK

This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Cotterell, Tom F. (2013) A new assemblage of manganese silicates in the Lower Cambrian manganese ore bed, Harlech, Merionethshire, Wales. Journal of the Russell Society, 16. 39-51
Cotterell, Tom F., Hubbard, Neil (2013) Franklinphilite in veinlets in the Lower Cambrian manganese ore bed, Harlech, Merionethshire, Wales. Journal of the Russell Society, 16. 51-59
museum.wales (n.d.) https://museum.wales/mineralogy-of-wales/database/?mineral=450&name=Franklinphilite
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