Your Blogs are 'top notch' Andrew. 10 out of 10.
When I was a teen in the 1950s my mates and I lived on the Winderemere Cres estate between the long gone Slag Heap and the Pumphouse Lake.
We sometimes went to Wardley Quarry which was just a couple of hundred yards south of Bill Quay Bridge which carried the main road to Pelaw , Heworth etc.
The water filled quarry was very deep and the view on the photo below is looking towards Mill Lane half a mile passed that line of trees.
I've swam in it & many years later I would have been 1200 ft below it when I was an apprentice 'Colliery Mechanic' at Wardley Colliery 2 mins south of it.

We lived at Grasmere Road near Windermere Ave and close to the lakes. I used to cycle through Monkton Village to school. The slag heap was always visible . Jean McIntosh and I used to climb it sit on the top and have a "swear day".

The works closed in 1968. At the peak they turned out 44,000 per week. The clay I believe was called Etruria Marl which is a great clay to make facing bricks and plentiful around the UK.