Wheal Sisters was also established on the same mineral lode to the east. Originally launched around 1810 under the name Wheal Duchy, the mine initially targeted copper ore. However, during prospecting operations, the discovery of silver ore became apparent, likely linked with a north-south crosscourse. Descriptions note the lode width reaching up to 31 centimeters, with the silver ore vein extending up to 15 centimeters wide. This silver deposit was first encountered at the adit level, extending downwards to a depth of 55 meters over a length of 5.5 meters within the lode. The silver deposit consisted of various minerals, including native silver, pyrargyrite, acanthite, galena, and siderite. Additionally, records mention the presence of grey and black sulphides of silver and antimony, although their exact nature remains unspecified.

Wheal Duchy ceased operations in 1816 but resumed activities in 1833 under the name Wheal Brothers. During investigations at the 30-fathom level, a significant quantity of silver ore was discovered in the stopes. Interestingly, the previous mine owners had seemingly overlooked this as silver ore. Within a mere three months, nearly £6000 worth of silver ore had been extracted. By 1874, the mine was operating in conjunction with the Silver Valley mine, which had been active since at least 1852. Recorded production from Wheal Duchy amounted to 200 tons of silver ore.

1833 1873-1879