Silver Valley Mine (William and Mary Worth Mine; incl. Ashburton Mine), Sevenstones, Calstock, Cornwall, England, UKi

Regional Level Types
Silver Valley Mine (William and Mary Worth Mine; incl. Ashburton Mine)	Mine (Abandoned)
Sevenstones	- not defined -
Calstock	Civil Parish
Cornwall	County
England	Constituent Country
UK	Country

An old silver and lead mine in a small valley on the southeast slope of Kit Hill, which was started in 1815 and worked until 1855. It was earlier known as William and Mary Worth Mine and was worked for some time together with Wheal Brothers. The sett extended on both sides of the valley, but the workings were mostly located on its eastern side (in Calstock parish). The workings on its western side were also known as Ashburton Mine. The grid reference marks the approximate location of the shaft.

The lode was said to be an extension of the Wheal Brothers lode, but its position is not known. A record of development works undertaken on the property in 1852 describes the lode as being 4 ft wide at the 14-fathom level, with a 6 inch (15 cm) leader of argentiferous ore yielding 200 ounces of silver per ton.

In 1912 and 1918, the property was prospected for tin and tungsten, but interest was focussed on another lode, called Goodluck Lode (possibly a westward extension of Goodluck Lode of Harrowbarrow Mine). It was composed of iron-rich chlorite with bands of quartz and contained traces of cassiterite, scattered spots of sulfides and bunches of bladed wolframite crystals to 1 inch in length. In 1943, when tungsten was in demand, the mine was reopened. The adit was cleared and extended and a crosscut driven from its western end that connected to Goodluck Lode. These workings were mainly on the west side of the valley (in Callington parish). Near the eastern end of the adit, wolframite was found occupying a 15 cm wide vein. Rich ores, however, were very unevenly distributed and the average values were below one percent for both tin and tungsten. The project was abandoned without having raised any ores.

The only recorded output of Silver Valley Mine is for 9 tons of 77% lead ore in 1852.

Geochronology

Geologic Time				Rocks, Minerals and Events
Phanerozoic
	Paleozoic
		Permian
			Guadalupian	ⓘ Major polymetallic mineralization ~270 Ma Cornwall, England, UK
			Cisuralian	ⓘ Porphyry dikes intruded (latest age) ~275 Ma Cornwall, England, UK ⓘ Greisenization (latest age) ~280 Ma Cornwall, England, UK ⓘ Porphyry dikes intruded (earliest age) ~280 Ma Cornwall, England, UK ⓘ Formation of metallized pegmatites ~285 Ma Cornwall, England, UK ⓘ Greisenization (earliest age) ~285 Ma Cornwall, England, UK ⓘ Emplacement of major plutons ~295 Ma Cornwall, England, UK

Other Regions, Features and Areas containing this locality

References