Removing the stone

Three different techniques were used to drill and split the large blocks of stone.  Over the quarry’s five decades of operation, hand drilling was replaced with steam drilling, which in turn was replaced in the mid 1920’s with compressed air drilling fed by aboveground pipes. The introduction of new drilling and splitting methods led to a one third increase in the amount of marketable stone the quarry was able to produce.

Source: Cathedral of Saint John the Divine Archives


Invented about 1800, this splitting method involved hand, and later machine-drilling a row of small, closely-spaced holes a few inches deep, placing iron wedge and feather tools in the holes, and tapping across the row of wedges until pressure split the stone, ideally on a flat plane. This method was used for quarrying and splitting into smaller blocks. Shallow “dog holes” chipped in opposite sides of the blocks provided grip for lifting hooks.

Wedge and feather splitting | Source: Peggy Perazzo, Stone Quarries & Beyond, Paul E. Wood Collection
Wedge and feather splitting | Source: Milestone Heritage Consulting
Quarrymen using a quarry bar on the ledge as a guide to make sure the holes drilled by the drill mounted to the bar are all drilled on the same plane so the stone splits straight | Source: Milestone Heritage Consulting

This uncommon method used wedge and feather splitting with alternating short and long holes. Steam-powered mechanical drills for long hole drilling were invented in the 1870s and were replaced after 1900 with compressed air models. At Mohegan, granite was difficult to split on flat, perpendicular planes, wasting the limited supply of golden granite. Deep hole splitting controlled the splitting, resulting in flatter planes, less waste and more usable stone.

Deep hole splitting | Source: Milestone Heritage Consulting

A tripod air drill used for deep hole splitting | Source: Milestone Heritage Consulting

This efficient mechanized method for extracting large blocks involved drilling rows of closely-spaced holes with a compressed air drill mounted on a horizontal bar, and then using a wide “broaching” bit to drill out the webs between the holes. A few strategically-placed blasting powder charges freed the block from the quarry wall. Broach channeling was faster and lower in cost than other splitting methods. It also helped the Mohegan Quarry conserve the most desirable stone.

Broach channeling | Source: Milestone Heritage Consulting
Broach channeling | Source: Milestone Heritage Consulting

Quarrying generated large quantities of “grout,” a Scottish word for rock rejected for poor splitting or quality. Workers lifted grout from the pit with derricks and discarded it in grout piles. The largest piles, extending downhill from the pit, were built using short railways running along their tops.

A blacksmith shop housed a forge, anvil and tools for repairing equipment. Among the blacksmith’s most important tasks was sharpening tools including worn rock drill bits. This skilled job was done entirely by hand until Grenci & Ellis installed a compressed air-powered drill sharpener in the mid-1920s.

A typical blacksmith shop illustrating blacksmiths heating drills in a forge at left and reshaping the chisel-like bits in a sharpening machine at right | Source: Milestone Heritage Consulting

Read about the next step in the quarrying process: Lifting the Stone