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Megiliggar Rocks (Tremearne pegmatite), Breage, Cornwall, England, UKi
| Regional Level Types | |
|---|---|
| Megiliggar Rocks (Tremearne pegmatite) | Outcrop |
| Breage | Civil Parish |
| Cornwall | County |
| England | Constituent Country |
| UK | Country |
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Latitude & Longitude (WGS84):
50° 5' 31'' North , 5° 20' 49'' West
Latitude & Longitude (decimal):
UK National Grid Reference:
SW607266
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Breage | 471 (2017) | 2.1km |
| Porthleven | 3,059 (2017) | 2.4km |
| Germoe | 175 (2017) | 3.4km |
| Helston | 12,184 (2017) | 5.6km |
| Leedstown | 267 (2017) | 7.6km |
The spectacular topaz granite sheets on the southern margin of the Tregonning-Godolphin Granite at Megiliggar Rocks, just north of Porthleven.
Megiliggar is famous for spectacular horizontal granite sheets exposed in the cliffs, where magmas from the adjacent Tregonning Granite pluton have injected in to the surrounding slate host rock. Local fisherman know this landmark as “stripy cliffs” for obvious reasons. There is a stark contrast between the pale yellow topaz granite and dark grey Mylor Slate Formation.
These magmas were super-saturated with volatiles and incompatible elements such as lithium, fluorine and phosphorus. As the magma in the sheets crystallised the interaction of melt, crystals, and hydrothermal fluids created some intricate structures, textures and mineralogy, elucidating a complex magmatic-hydrothermal evolution.
The sheets intruded laterally, sourced from evolved magmas pooling in the roof of the Tregonning Godolphin granite pluton to the north and west of Megiliggar. The sheets are in excess of 3 m thick.Even though the sheets are sub-horizontal they don’t actually follow bedding, which has been heavily folded in the Mylor Slate Formation. Instead, they probably followed other planes of weakness such as low angle faults and fractures along foliation planes.
This area is a site of special scientific interest and protected under the geological conservation reviews. It is also quite difficult to get to, made even more so when the access was washed away by storms in 2014.
(Description by Dr S. Hughes, Camborne School of Mines, University of Exeter)
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsCommodity List
This is a list of exploitable or exploited mineral commodities recorded at this locality.Mineral List
17 valid minerals.
Detailed Mineral List:
| ⓘ Albite Formula: Na(AlSi3O8) |
| ⓘ Alluaudite Formula: (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| ⓘ Amblygonite Formula: LiAl(PO4)F |
| ⓘ 'Apatite' Formula: Ca5(PO4)3(Cl/F/OH) |
| ⓘ Fluorapatite Formula: Ca5(PO4)3F |
| ⓘ Fluorapatite var. Manganese-bearing Fluorapatite Formula: (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| ⓘ Fluorite Formula: CaF2 |
| ⓘ 'Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series' |
| ⓘ 'Lepidolite' |
| ⓘ Löllingite Formula: FeAs2 |
| ⓘ Muscovite Formula: KAl2(AlSi3O10)(OH)2 References: |
| ⓘ Muscovite var. Gilbertite Formula: KAl2(AlSi3O10)(OH)2 References: |
| ⓘ 'Natromontebrasite' |
| ⓘ Nontronite Formula: Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| ⓘ Orthoclase Formula: K(AlSi3O8) |
| ⓘ Quartz Formula: SiO2 |
| ⓘ Rutile Formula: TiO2 |
| ⓘ Rutile var. Strüverite Formula: (Ti,Ta,Fe)O2 |
| ⓘ Schorl Formula: NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| ⓘ Topaz Formula: Al2(SiO4)(F,OH)2 |
| ⓘ Triphylite Formula: LiFe2+PO4 |
| ⓘ Triplite Formula: Mn2+2(PO4)F |
| ⓘ Vivianite Formula: Fe2+Fe2+2(PO4)2 · 8H2O |
| ⓘ Zwieselite Formula: Fe2+2(PO4)F |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Löllingite | 2.EB.15a | FeAs2 |
| Group 3 - Halides | |||
| ⓘ | Fluorite | 3.AB.25 | CaF2 |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | 'Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series' | 4.. | |
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| ⓘ | Rutile | 4.DB.05 | TiO2 |
| ⓘ | var. Strüverite | 4.DB.05 | (Ti,Ta,Fe)O2 |
| Group 8 - Phosphates, Arsenates and Vanadates | |||
| ⓘ | Triphylite | 8.AB.10 | LiFe2+PO4 |
| ⓘ | Alluaudite | 8.AC.10 | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| ⓘ | Amblygonite | 8.BB.05 | LiAl(PO4)F |
| ⓘ | Triplite | 8.BB.10 | Mn2+2(PO4)F |
| ⓘ | Zwieselite | 8.BB.10 | Fe2+2(PO4)F |
| ⓘ | Fluorapatite | 8.BN.05 | Ca5(PO4)3F |
| ⓘ | var. Manganese-bearing Fluorapatite | 8.BN.05 | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| ⓘ | Vivianite | 8.CE.40 | Fe2+Fe2+2(PO4)2 · 8H2O |
| Group 9 - Silicates | |||
| ⓘ | Topaz | 9.AF.35 | Al2(SiO4)(F,OH)2 |
| ⓘ | Schorl | 9.CK.05 | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| ⓘ | Muscovite var. Gilbertite | 9.EC.15 | KAl2(AlSi3O10)(OH)2 |
| ⓘ | 9.EC.15 | KAl2(AlSi3O10)(OH)2 | |
| ⓘ | Nontronite | 9.EC.40 | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| ⓘ | Orthoclase | 9.FA.30 | K(AlSi3O8) |
| ⓘ | Albite | 9.FA.35 | Na(AlSi3O8) |
| Unclassified | |||
| ⓘ | 'Lepidolite' | - | |
| ⓘ | 'Natromontebrasite' | - | |
| ⓘ | 'Apatite' | - | Ca5(PO4)3(Cl/F/OH) |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Muscovite var. Gilbertite | KAl2(AlSi3O10)(OH)2 |
| H | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| H | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| H | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| H | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| H | ⓘ Topaz | Al2(SiO4)(F,OH)2 |
| H | ⓘ Vivianite | Fe2+Fe22+(PO4)2 · 8H2O |
| H | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Li | Lithium | |
| Li | ⓘ Amblygonite | LiAl(PO4)F |
| Li | ⓘ Triphylite | LiFe2+PO4 |
| B | Boron | |
| B | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | Oxygen | |
| O | ⓘ Albite | Na(AlSi3O8) |
| O | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| O | ⓘ Amblygonite | LiAl(PO4)F |
| O | ⓘ Fluorapatite | Ca5(PO4)3F |
| O | ⓘ Muscovite var. Gilbertite | KAl2(AlSi3O10)(OH)2 |
| O | ⓘ Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series | |
| O | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| O | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| O | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| O | ⓘ Orthoclase | K(AlSi3O8) |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Rutile | TiO2 |
| O | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | ⓘ Rutile var. Strüverite | (Ti,Ta,Fe)O2 |
| O | ⓘ Topaz | Al2(SiO4)(F,OH)2 |
| O | ⓘ Triphylite | LiFe2+PO4 |
| O | ⓘ Triplite | Mn22+(PO4)F |
| O | ⓘ Vivianite | Fe2+Fe22+(PO4)2 · 8H2O |
| O | ⓘ Zwieselite | Fe22+(PO4)F |
| O | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| F | Fluorine | |
| F | ⓘ Amblygonite | LiAl(PO4)F |
| F | ⓘ Fluorapatite | Ca5(PO4)3F |
| F | ⓘ Fluorite | CaF2 |
| F | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| F | ⓘ Topaz | Al2(SiO4)(F,OH)2 |
| F | ⓘ Triplite | Mn22+(PO4)F |
| F | ⓘ Zwieselite | Fe22+(PO4)F |
| F | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Na | Sodium | |
| Na | ⓘ Albite | Na(AlSi3O8) |
| Na | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| Na | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| Na | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Mg | Magnesium | |
| Mg | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| Al | Aluminium | |
| Al | ⓘ Albite | Na(AlSi3O8) |
| Al | ⓘ Amblygonite | LiAl(PO4)F |
| Al | ⓘ Muscovite var. Gilbertite | KAl2(AlSi3O10)(OH)2 |
| Al | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Al | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| Al | ⓘ Orthoclase | K(AlSi3O8) |
| Al | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Al | ⓘ Topaz | Al2(SiO4)(F,OH)2 |
| Si | Silicon | |
| Si | ⓘ Albite | Na(AlSi3O8) |
| Si | ⓘ Muscovite var. Gilbertite | KAl2(AlSi3O10)(OH)2 |
| Si | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Si | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| Si | ⓘ Orthoclase | K(AlSi3O8) |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Si | ⓘ Topaz | Al2(SiO4)(F,OH)2 |
| P | Phosphorus | |
| P | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| P | ⓘ Amblygonite | LiAl(PO4)F |
| P | ⓘ Fluorapatite | Ca5(PO4)3F |
| P | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| P | ⓘ Triphylite | LiFe2+PO4 |
| P | ⓘ Triplite | Mn22+(PO4)F |
| P | ⓘ Vivianite | Fe2+Fe22+(PO4)2 · 8H2O |
| P | ⓘ Zwieselite | Fe22+(PO4)F |
| P | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Cl | Chlorine | |
| Cl | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| Cl | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| K | Potassium | |
| K | ⓘ Muscovite var. Gilbertite | KAl2(AlSi3O10)(OH)2 |
| K | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| K | ⓘ Orthoclase | K(AlSi3O8) |
| Ca | Calcium | |
| Ca | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| Ca | ⓘ Fluorapatite | Ca5(PO4)3F |
| Ca | ⓘ Fluorite | CaF2 |
| Ca | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| Ca | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Ti | Titanium | |
| Ti | ⓘ Rutile | TiO2 |
| Ti | ⓘ Rutile var. Strüverite | (Ti,Ta,Fe)O2 |
| Mn | Manganese | |
| Mn | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| Mn | ⓘ Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series | |
| Mn | ⓘ Fluorapatite var. Manganese-bearing Fluorapatite | (Ca,Mn2+)5(PO4)3(F,Cl,OH) or Ca5([P,Mn5+]O4)3(F,Cl,OH) |
| Mn | ⓘ Triplite | Mn22+(PO4)F |
| Fe | Iron | |
| Fe | ⓘ Alluaudite | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| Fe | ⓘ Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series | |
| Fe | ⓘ Löllingite | FeAs2 |
| Fe | ⓘ Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| Fe | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Fe | ⓘ Rutile var. Strüverite | (Ti,Ta,Fe)O2 |
| Fe | ⓘ Triphylite | LiFe2+PO4 |
| Fe | ⓘ Vivianite | Fe2+Fe22+(PO4)2 · 8H2O |
| Fe | ⓘ Zwieselite | Fe22+(PO4)F |
| As | Arsenic | |
| As | ⓘ Löllingite | FeAs2 |
| Ta | Tantalum | |
| Ta | ⓘ Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series | |
| Ta | ⓘ Rutile var. Strüverite | (Ti,Ta,Fe)O2 |
Geochronology
| Geologic Time | Rocks, Minerals and Events | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Phanerozoic | ||||||||||||||||||||||
| Paleozoic | ||||||||||||||||||||||
| Permian | ||||||||||||||||||||||
| Guadalupian |
| |||||||||||||||||||||
| Cisuralian |
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Other Regions, Features and Areas containing this locality
British and Irish IslesGroup of Islands
Eurasian PlateTectonic Plate
- Rheno-Hercynian BeltOrogenic Belt
EuropeContinent
UK
- England
- Cornwall
- Mount's Bay Mining DistrictMining District
- Devon and Cornwall metalliferous mining districtMining District
- Cornwall
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Megiliggar Rocks, Breage, Cornwall, England, UK