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Downrew Quarry, Bishop's Tawton, North Devon, Devon, England, UKi
| Regional Level Types | |
|---|---|
| Downrew Quarry | Quarry |
| Bishop's Tawton | Civil Parish |
| North Devon | District |
| Devon | County |
| England | Constituent Country |
| UK | Country |
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Latitude & Longitude (WGS84):
51° 2' 47'' North , 4° 1' 23'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Swimbridge | 669 (2018) | 3.7km |
| Barnstaple | 31,616 (2018) | 4.5km |
| Goodleigh | 450 (2018) | 5.0km |
| Chittlehampton | 239 (2018) | 6.6km |
| Fremington | 4,310 (2018) | 8.3km |
This small, private quarry, occasionally worked for aggregates lies in the uppermost unit of the Codden Hill Cherts. The rock here varies between friable and moderately competent, and is intensely fractured.
The largely carbonate depleted mud and siltstones contain occasional fossils and frequent, lenticular phosphatic nodules (presumably coprolites comprising mainly fish bones and chitin) many of which have undergone variable dissolution.
The rock is variously stained with red, yellow and brown iron oxides/hydroxides; dendritic manganese minerals are frequent. In parts, the quarry exhibits very local and intense phosphate mineralisation.
The quarry is occasionally worked for aggregate. The farmer who owns the quarry lives nearby and he will ask anyone who has not asked permission to leave.
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
8 valid minerals.
Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
| ⓘ Beraunite ? Formula: Fe3+6(PO4)4O(OH)4 · 6H2O Habit: Massive, bladed masses. Colour: reddish-brown to clove brown Description: Some reddish-brown areas of a small number of specimens show the bladed forms resembling those of eleonorite.
Further work is required for confirmation. References: |
| ⓘ Cacoxenite Formula: Fe3+24AlO6(PO4)17(OH)12 · 75H2O Habit: massive, botryoidal, encrusting Colour: yellow Description: Cacoxenite is found as a bright yellow encrustation in fractures in the rock of the quarry, often in association with porous quartz veins.
Where it is found, it is locally abundant but is absent through most of the quarry.
Larger plates showing the phosphatic mineralisation vary across the suface between clove-brown and bright yellow, occasionally to orange and red. The cacoxenite is generally between a deep yellow-brown and bright yellow. References: |
| ⓘ 'Manganese Oxides' References: |
| ⓘ 'Manganese Oxides var. Manganese Dendrites' Habit: Dendritic - coarsely crystalline to lacy dendritic encrustations. Colour: Black Description: The development of manganese dendrites is particularly varied in this quarry - ranging from coarse, tangible crystals infilling fracture voids down to delicate, mossy developments across the siltstone surfaces.
In places, these developments do present a particular aesthetic appeal.
References: |
| ⓘ Metavivianite ? Formula: Fe2+Fe3+2(PO4)2(OH)2 · 6H2O Habit: blased masses Colour: dark green Description: A few areas of phosphatic encrustation show the colour and approximate form of metavivianite.
Further work is required. References: |
| ⓘ Opal Formula: SiO2 · nH2O References: |
| ⓘ Opal var. Common Opal Formula: SiO2 · nH2O Habit: none: massive Colour: white to off-white Fluorescence: none Description: Redeposited silica tubes formed in cracks in the Codden Hill Cherts which host a number of phosphate species.
These thin-walled tubes appear to have formed in much the same way as speleothem 'straws', and various walls and ramifications appear across the rock surfaces. These same cracks also play host to the various phosphate minerals found at this location. References: |
| ⓘ Rockbridgeite ? Formula: (Fe2+0.5Fe3+0.5)2Fe3+3(PO4)3(OH)5 References: |
| ⓘ Strengite ? Formula: FePO4 · 2H2O Habit: botryoidal, encrusting; massive Colour: pale purple Description: Areas of purple phosphatic encrustations strongly resemble strengite. References: |
| ⓘ Variscite ? Formula: AlPO4 · 2H2O Habit: botryoidal; encrusting Colour: white Description: Tiny, pale hemispheres and white encrustations have been tentatively placed as variscite.
Variscite has been previously reported (unconfirmed) from this location. References: |
| ⓘ Wavellite Formula: Al3(PO4)2(OH)3 · 5H2O Habit: Radial hemispheres, botryoidal Colour: bottle green to black Description: Small clusters of generally dark hemispheres lining a cavity formerly filled with phosphatic clay. Other minerals peresent in this specimen are manganese oxides, cacoxenite and other unidentified (phosphate) minerals.
The specimen was removed in the process of extracting cacoxenite plates from the quarry wall. References: |
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Opal | 4.DA.10 | SiO2 · nH2O |
| ⓘ | var. Common Opal | 4.DA.10 | SiO2 · nH2O |
| Group 8 - Phosphates, Arsenates and Vanadates | |||
| ⓘ | Rockbridgeite ? | 8.BC.10 | (Fe2+0.5Fe3+0.5)2Fe3+3(PO4)3(OH)5 |
| ⓘ | Strengite ? | 8.CD.10 | FePO4 · 2H2O |
| ⓘ | Variscite ? | 8.CD.10 | AlPO4 · 2H2O |
| ⓘ | Metavivianite ? | 8.DC.25 | Fe2+Fe3+2(PO4)2(OH)2 · 6H2O |
| ⓘ | Beraunite ? | 8.DC.27 | Fe3+6(PO4)4O(OH)4 · 6H2O |
| ⓘ | Cacoxenite | 8.DC.40 | Fe3+24AlO6(PO4)17(OH)12 · 75H2O |
| ⓘ | Wavellite | 8.DC.50 | Al3(PO4)2(OH)3 · 5H2O |
| Unclassified | |||
| ⓘ | 'Manganese Oxides var. Manganese Dendrites' | - | |
| ⓘ | '' | - | |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Beraunite | Fe63+(PO4)4O(OH)4 · 6H2O |
| H | ⓘ Cacoxenite | Fe243+AlO6(PO4)17(OH)12 · 75H2O |
| H | ⓘ Metavivianite | Fe2+Fe23+(PO4)2(OH)2 · 6H2O |
| H | ⓘ Opal | SiO2 · nH2O |
| H | ⓘ Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe33+(PO4)3(OH)5 |
| H | ⓘ Strengite | FePO4 · 2H2O |
| H | ⓘ Variscite | AlPO4 · 2H2O |
| H | ⓘ Wavellite | Al3(PO4)2(OH)3 · 5H2O |
| H | ⓘ Opal var. Common Opal | SiO2 · nH2O |
| O | Oxygen | |
| O | ⓘ Beraunite | Fe63+(PO4)4O(OH)4 · 6H2O |
| O | ⓘ Cacoxenite | Fe243+AlO6(PO4)17(OH)12 · 75H2O |
| O | ⓘ Metavivianite | Fe2+Fe23+(PO4)2(OH)2 · 6H2O |
| O | ⓘ Opal | SiO2 · nH2O |
| O | ⓘ Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe33+(PO4)3(OH)5 |
| O | ⓘ Strengite | FePO4 · 2H2O |
| O | ⓘ Variscite | AlPO4 · 2H2O |
| O | ⓘ Wavellite | Al3(PO4)2(OH)3 · 5H2O |
| O | ⓘ Opal var. Common Opal | SiO2 · nH2O |
| Al | Aluminium | |
| Al | ⓘ Cacoxenite | Fe243+AlO6(PO4)17(OH)12 · 75H2O |
| Al | ⓘ Variscite | AlPO4 · 2H2O |
| Al | ⓘ Wavellite | Al3(PO4)2(OH)3 · 5H2O |
| Si | Silicon | |
| Si | ⓘ Opal | SiO2 · nH2O |
| Si | ⓘ Opal var. Common Opal | SiO2 · nH2O |
| P | Phosphorus | |
| P | ⓘ Beraunite | Fe63+(PO4)4O(OH)4 · 6H2O |
| P | ⓘ Cacoxenite | Fe243+AlO6(PO4)17(OH)12 · 75H2O |
| P | ⓘ Metavivianite | Fe2+Fe23+(PO4)2(OH)2 · 6H2O |
| P | ⓘ Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe33+(PO4)3(OH)5 |
| P | ⓘ Strengite | FePO4 · 2H2O |
| P | ⓘ Variscite | AlPO4 · 2H2O |
| P | ⓘ Wavellite | Al3(PO4)2(OH)3 · 5H2O |
| Fe | Iron | |
| Fe | ⓘ Beraunite | Fe63+(PO4)4O(OH)4 · 6H2O |
| Fe | ⓘ Cacoxenite | Fe243+AlO6(PO4)17(OH)12 · 75H2O |
| Fe | ⓘ Metavivianite | Fe2+Fe23+(PO4)2(OH)2 · 6H2O |
| Fe | ⓘ Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe33+(PO4)3(OH)5 |
| Fe | ⓘ Strengite | FePO4 · 2H2O |
Geochronology
Mineralization age: Carboniferous : 341 Ma to 326.4 ± 1.6 MaImportant note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.
| Geologic Time | Rocks, Minerals and Events | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Phanerozoic | ||||||||||||||||||||||
| Paleozoic | ||||||||||||||||||||||
| Carboniferous | ||||||||||||||||||||||
| Mississippian |
| |||||||||||||||||||||
Other Regions, Features and Areas containing this locality
British and Irish IslesGroup of Islands
Eurasian PlateTectonic Plate
- Rheno-Hercynian BeltOrogenic Belt
EuropeContinent
UK
- England
- Devon and Cornwall metalliferous mining districtMining District
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Downrew Quarry, Bishop's Tawton, North Devon, Devon, England, UK