Quarries

Field Boulders

About 10,000 years ago, the glaciers covered most of New England. As the glaciers slowly moved southward, they picked up large chunks of rock from the mountains and moved them many miles to the south. When the glaciers eventually melted, these large boulders were left behind. Geologists called these boulder “glacial erratics”.

The colonists who arrived in Massachusetts in the 1600’s used these glacial erratics as an easy source of building materials for foundations, chimneys, and stone walls. The smaller stones were used as it, while the larger stone were split apart using several simple but rather crude quarrying techniques. By the mid-1700’s the locally available supply of glacial erratics had become somewhat depleted in Boston and other neighboring towns like Quincy. The problem was serious enough for town officials to ban the removal of any more stone from the town’s common lands.

Early farmers who had established farms far from the city limits found a very different problem. They had too many boulders with some to large to move whole. The New-England Farmer: or Georgical Dictionary published in 1790 offered the following advice to farmers, “Stones that are very large, and which cannot with ease be removed whole, may be blown to pieces with gunpowder.” The book also suggested a second method of removing field boulders, “.. another method of breaking rocks, which ought to be generally known, and which sometimes turns out cheaper, is this: Drill two holes in a stone, ranging with the grain, when that can be discovered with the eye. Then filling each hole with two semi-cylindrical peices of iron, drive a long steel wedge between them. The stone will thus split open. And commonly, very regular shaped pieces for building may be obtained.” By the mid 1800’s some farmers were supplementing their income by quarrying field boulders on their farms during the off seasons.

Field boulder split using an early plug & feather method. The foundation is circa 1790-1825.
South Hampton, NH

Glacial field boulder split into quarter sections using the later version of the plug & feather method. The stone from this boulder was being used for renovations of a nearby farm house foundation. It was quarried circa 1825-1850.

Ledge Quarries

Ledge quarries are places were exposed bedrock, usually on hillsides, was quarried for usuable bars of rock. Generally, only the first ten feet (or less) of the surface ledge was quarried. The exposed bedrock many times had well defined fractures, both horizontal and vertical, that allowed for roughly rectangular blocks andf slabs of stone to be split off. It was a major improvement over glacial boulders whose splitting properties were unpredictable. Ledge quaries post date 1803 and used into the 1870’s and possibly later. Ledge quarrying was made possible by major improvements in stone splitting methods introduced in 1803. Ledge quarry generally supplied stone for local building projects like foundations, stone walls, and culverts. Railroads in particular, made extensive use of surface ledge quarries for building culverts, bridge abutments, and other railroad related structures. These quarries can be found for the most part within a 100 yards of old railroad beds.

A mid-19th century surface ledge quarry near an abandoned railroad line. Slabs from this quarried were used in culverts for the railroad bed. The surface ledge had horizontal fractures at regular intervals. This allowed for uniform thickness of slabs to be quarried. This also creates the stepped like appearance of the quarry.

Pit Quarries

Pit quarries are the deep modern quarries most people are familar with. These deep pit quarries exploited the superior grades of stone found deeper in the bedrock. In fact, most of these pit quarries would blast away the top 20 or more feet of the top surface ledge due to its poor quality. Stone from these quarries was used for commercial and government buildings, public monuments, and other important stone edifices.

Deep pit quarries are a post 1825 phenomon. They were made possible by major innovations in hoisting and transportation of large blocks of stone developed during the construction of the Bunker Hill Monument (completed in 1825) in Boston, MA. Stone for the mounument was quarried in Quincy, MA. America’s first railroad that was horse drawn was introduced to haul stone out of this quarry.

Deep Pit Quarry - Babson Farm Quarry, Halibut State Park, Rockport, MA.

Source: The information on stone splitting and quarrying comes from the book The Art of Splitting Stone. The book discusses the various methods, tools, and types of quarries in greater depth. In additional, it quotes source documents and discusses archaeological sites important to the study of early New England quarrying. It is excellent resource on the subject.