Lessons from Coastal Maine Granite Quarries
by Lester C. Kenway of Trail Services

The Maine Coast was home to a flourishing granite industry throughout the 1800’s and well into the first half of the 20th century. High quality gray granite, formed from igneous intrusions of the Acadian Progeny during the Devonian Period, was found in numerous locations along the coast. Quarries were opened in Rockland, Hurricane Island, Stoning-ton, Black Island, Mt. Desert, Sultan, and other coastal villages where quarried blocks of stone could be loaded onto schooners, and shipped to the growing cities of Boston, New York, and Philadelphia to be used in the construction of public buildings, sidewalks and streets.
These quarries cut slabs of granite, up to 20 feet thick, which were then cut into building stone, steps, facade, monuments, curbing and paving stones. The methods were clever and exploited the character of the material. Initially, all work was done by hand, later supplemented by pneumatic tools.
The demand for granite products was all but eliminated by the move to reinforced concrete architecture after World War II. Almost all of the Maine quarries are now closed, with a handful of craftsmen keeping the knowledge of these techniques alive.
Acadia National Park is one location where these skills are still in use. Acadia is engaged in a long term program dedicated to preserve historic stone work throughout its trail system. This project seeks to duplicate high standard stone trail work completed by stone masons, and CCC crews during the first half of the 20th century. The Acadia Trail Crew, in partnership with Gibbon Buell, of Sultan Quarries, has incorporated these traditional techniques into its current methods. The objective of stone cutting is to produce, clean, straight splits in the stone in order to provide useful pieces to build with. A summary of these methods follows:

1. Read the grain: This refers to discovering the three primary directions of likely breakage in a piece of granite by assessing evidence shown in the shape and surface character of the stone. These directions were sometimes referred to as “The Lift”(a plane parallel to the surface of the earth), “The Drift” (a plane perpendicular to the Lift), and “The Hard Way” (a plane at right angles to both the Lift and the Drift). Discovering these directions when stone is still in place in the earth is quite straightforward. Reading grain becomes more challenging when boulders are tumbled down slopes or relocated by glaciers. Evidence of the three directions can be discovered as follows:

1. Flakes on a rock often run parallel a splitting plane
2. Small ledges may indicate one of the planes
3. Long cracks may indicate one of the planes
4. The largest flat surface of the boulder is likely to be either parallel or perpendicular to one of the planes.

If a boulder is very rounded, evidence will be hard to find. Look especially for 2 or more indicators to confirm the same splitting direction. These indicators do not have to point to the exact same spot, since numerous potential breaking planes exist in each of the three directions.

2. Plan the split- The 50% rule: Since granite is a crystalline material, it tends to separate along the path of least resistance. If you should try to take a thin slice from one end, the crack will tend to run out the parallel surface, as opposed to running through to the far side of the rock. This will produce a large unattractive “spalled” surface on the rock, and a worthless curved flake. The safest strategy is to cut each stone into halves. These halves can then be cut in half again, until stones of useable size are produced.

3. Score the line: Once the direction of split has been chosen, it is marked on the stone with crayon or chalk. Scoring means repeatedly striking along the line with a bevel edge tool. The scoring serves to send shocks through the crystalline stone, which weakens the stone along the chosen plane. The scoring greatly increases the likelihood of a successful split, and reduces the amount of force that needs to be applied with wedges to part of the stone. Small stones can be cut without using wedges at all. A tool called a rifting hammer can be used to score big stones. One person holds the rifter in place, while a second one strikes it with a hammer. The two workers score a line back and forth many times until a distinct groove is worn in the stone. Rifters are difficult to strike on a vertical surface, so a tool called a tracer can be used by one person to score a line. The tracer is like a wide chisel, and can be held with one hand and struck with a hammer. Tracers can also be used by themselves to cut smaller stones.

4. Drill holes for wedges: These holes can be drilled by hand with star drills (if you work in wilderness areas) or with various gas, electric or air powered drills. The holes need to be spaced evenly along the score line, and drilled in the same plane as has been defined by the scoring. Experience with size and type of stone will determine optimum spacing for wedges. Typical spacing for smaller sets ( 3/4″ - 1″) would be 4″ to 6″ apart, while spacing for large sets ( 1-1/4″ - 1-3/8″) would be 8″ to 12″ apart. The more sets of wedges used in a split, the more pushing power available to separate the stone.

• Holes should be drilled as deep as the straight part of the shim or feather. Shallow holes will result if the feathers’ being bent by the wedge (or plug).
• If holes are drilled deeper than the shim, the wedge can drive the shims down into the hole and straighten out the top of the shim.
• Feathers can be used to spoon stone dust out of holes, and to check the depth of the hole. Do not use a wedge to check the hole depth, since it will be difficult to get it out of a hole if you drop it in.

5. Place feathers and wedges and split stone:

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• All wedge sets are placed in the holes oriented so they all push together in the same plane in order to push the halves of stone apart.
• All wedges are driven with a hammer until they are “loaded”. This is indicated by each wedge emitting a tone or ringing sound. When all wedges are loaded, the stone is allowed to react to the pressure for 1 to 3 minutes.
• Wedges are driven equally, a little bit at a time. The sound of the tone of each wedge, when it is struck, can indicate the relative tightness of each wedge. If the wedges seem to be going hard, more scoring can be done between the wedges.
• Eventually, a crack will begin to show along a scored line. At this point, drive only one wedge, so other wedges can be retrieved. You can then drive a lone wedge into the crack and retrieve the remaining wedge set. The two halves of stone can be separated with pry bars.