Although of minor importance compared to Clogau and Gwynfynedd mines, Cefn Coed/Berthlwyd Mine was the forth richest of the gold mines in the Dolgelau gold belt, its greatest output was in the 1860s.

Cefn Coch was often worked jointly with the nearby Berthlwyd Mine (SH722235) that follows the same lode. As the histories of the two mines are difficult to disentangle, they have been grouped together here.

Mining first took place at Berthlwyd around 1843, with gold being discovered about 1845. Gold was discovered in the Cefn Coch section in 1862. Although substantial quantities of ore were produced prior to 1862, there are output figures available. From 1862-1865, when working ceased, 1900 tons of ore yielded 648 ounces of gold. There was then an unsuccessful attempt at reworking from about 1873-1877.

Although little was done at Berthlwyd after 1866, Cefn Coch was reopened in 1889 on the back of the 1887 gold rush, its most successful year during its final opening being in 1894 when 360 tons of ore produced 180 ounces of gold.

The total recorded output between 1862 and 1912 was 2661 tons of gold ore, which produced 1392 ounces of gold. The mine finally closed in 1914

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Mineral List

ⓘ Chalcopyrite

7 valid minerals.

Detailed Mineral List:

ⓘ Chalcopyrite

Formula: CuFeS₂

References:

ref: Goldmining in Western Merioneth, T. A. Morrison (undated)

ⓘ Cobaltite

Formula: CoAsS

References:

Day, Harry (1999) BMS Database, British Micromount Society.

ⓘ Dolomite

Formula: CaMg(CO₃)₂

References:

National Museum of Wales datebase

ⓘ Galena

Formula: PbS

References:

ref: Goldmining in Western Merioneth, T. A. Morrison (undated)

ⓘ Native Gold

Formula: Au

References:

R. E. Bevins (1988) Sixth Supplementary List of British Isles Minerals (Welsh). Mineralogical Magazine 52:121-124

ⓘ Native Gold var. Electrum

Formula: (Au,Ag)

References:

R. E. Bevins (1988) Sixth Supplementary List of British Isles Minerals (Welsh). Mineralogical Magazine 52:121-124

ⓘ Sphalerite

Formula: ZnS

References:

ref: Goldmining in Western Merioneth, T. A. Morrison (undated)

ⓘ Tellurobismuthite

Formula: Bi₂Te₃

References:

Day, Harry (1999) BMS Database, British Micromount Society.

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
ⓘ	Native Gold var. Electrum	1.AA.05	(Au,Ag)
ⓘ		1.AA.05	Au
Group 2 - Sulphides and Sulfosalts
ⓘ	Sphalerite	2.CB.05a	ZnS
ⓘ	Chalcopyrite	2.CB.10a	CuFeS₂
ⓘ	Galena	2.CD.10	PbS
ⓘ	Tellurobismuthite	2.DC.05	Bi₂Te₃
ⓘ	Cobaltite	2.EB.25	CoAsS
Group 5 - Nitrates and Carbonates
ⓘ	Dolomite	5.AB.10	CaMg(CO₃)₂

List of minerals for each chemical element

C	Carbon
C	ⓘ Dolomite	CaMg(CO₃)₂
O	Oxygen
O	ⓘ Dolomite	CaMg(CO₃)₂
Mg	Magnesium
Mg	ⓘ Dolomite	CaMg(CO₃)₂
S	Sulfur
S	ⓘ Chalcopyrite	CuFeS₂
S	ⓘ Cobaltite	CoAsS
S	ⓘ Galena	PbS
S	ⓘ Sphalerite	ZnS
Ca	Calcium
Ca	ⓘ Dolomite	CaMg(CO₃)₂
Fe	Iron
Fe	ⓘ Chalcopyrite	CuFeS₂
Co	Cobalt
Co	ⓘ Cobaltite	CoAsS
Cu	Copper
Cu	ⓘ Chalcopyrite	CuFeS₂
Zn	Zinc
Zn	ⓘ Sphalerite	ZnS
As	Arsenic
As	ⓘ Cobaltite	CoAsS
Ag	Silver
Ag	ⓘ Native Gold var. Electrum	(Au,Ag)
Te	Tellurium
Te	ⓘ Tellurobismuthite	Bi₂Te₃
Au	Gold
Au	ⓘ Native Gold var. Electrum	(Au,Ag)
Au	ⓘ Native Gold	Au
Pb	Lead
Pb	ⓘ Galena	PbS
Bi	Bismuth
Bi	ⓘ Tellurobismuthite	Bi₂Te₃

Other Regions, Features and Areas containing this locality

British and Irish IslesGroup of Islands

Eurasian PlateTectonic Plate

AvaloniaVolcanic Arc

EuropeContinent

Wales
- Cambrian MountainsMountain Range
- Gwynedd
  - Dolgellau Gold BeltBelt
- Snowdonia National ParkNational Park

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

Goldmining in Western Merioneth, T. A. Morrison (undated)

The Gold Mines of Merioneth, G.W. Hall (undated)

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