At the same time that scientists were beginning to differentiate and name rock units, the quarrymen working deep in the mines underneath Wren’s Nest would have developed their own naming system for the rocks they encountered. Working by candlelight, their names would have been based on basic features and the look of the rock. Experienced miners would have been able to tell the grade of rock they were mining from one look or perhaps even by feel alone.
Murchison lists some of the words used by the miners and quarrymen in his Silurian System:
- “Strong hanging stone”
- “Top sink”
- “Half-yard measure”
- “Strong grey measure”
- “The flints”
- “Silks measures”
- “bavin” and “rotch”
Some of the names we can only begin to guess at the meaning of, but it is not unreasonable to think that perhaps “Half-yard measure” would have been a band of limestone 18 inches thick, and “pricking” is described as a way-board of shale (blasting layer) so would perhaps have been drilled (pricked) with numerous holes which could be filled with black powder to blast layers of rock away from the walls of the mine.
We do know that “ballstone” referred to a dome-shaped mass of pure limestone which would have disrupted the bedding of the rock around it, and could sometimes have been very large, up to 6 metres high by 20 metres wide. We now refer to them as bioherms and we know that they represent the remains of small reefs similar to those found in tropical lagoons today, and here the reef-building organisms such as corals and stromatoporoids formed massive calcareous structures which would later be turned into limestone.
Today the science of lithostratigraphy deals with the naming of rock layers and formal names are assigned to these rock units such as the Upper Quarried Limestone Member.