Originally an alum shale quarry between 1776 and 1805.
In 1929 an aerial ropeway was installed to dump waste from the Spa Woods ironstone mine into the quarry, it was dismantled 1933-34 and moved to Upton Colliery.
The area is now heavily wooded so its difficult to interpret which spoil belongs to which phase.
Cass Rock Quarry
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I might have read somewhere that (very small) remnants of the aerial ropeway are to be found amongst the undergrowth. There are a couple of good photographs in one of Simon’s books of the ropeway in operation.
The bases of the supporting towers can be found if you have a thrash around, they became a lot more visible with the recent logging operations