Hi JM,
I also had a lot of Shale miners in my family.
The shale contained oil that was used to make Paraffin,candle wax,vasoline etc,. The shale was brought to the surface and baked.
The shale mines were mostly found in the Mid & West Lothian areas, hence the Red Slag heaps (bings), still seen to this day. The industry ceased around 1963.
On Google, under shale miners, there is a 'Historical Research Report', that has a lot of interviews with ex shale miners, very good and interesting reading, on all aspects of the shale miners & their way of life.
Iain