St. Day is located in a former mining area (which included Poldice, Tolcarne, Todpool, Creegbrawse and Crofthandy) and St Day accrued considerable wealth from mining.
St Day was a centre for the richest and perhaps most famous copper mining district in the world from the 16th century up to the 1830s. The population, wealth and activity in St Day declined steadily from about 1870 onwards, today the population is smaller than in 1841. It is now essentially a residential village with a population of 3,069 in 2001 (UK census).
The Wheal Gorland mine in St Day is the type locality for the minerals Chenevixite, Clinoclase, Cornwallite and Liroconite.
The parish was originally a chapelry of Gwennap but became independent in 1835. As early as the 13th century there was a chapel of the Holy Trinity at St Day and even earlier there had been one of St Day which was a great centre of pilgrimage. The saint commemorated here is probably the Breton Saint Dei.
One of the many maps available on A Vision of Britain through Time is one from the Ordnance Survey Series of 1900 illustrating the parish boundaries of Cornwall at the turn of the 20th century. This map blows up to show all the parishes and many of the small villages and hamlets.
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