A visit to the marble quarries at Pietrasanta

Photographs and text by Marc Levoy
November 20, 1998

CS 149 - Field Project in Computer Graphics, was created to allow undergraduates to work on Professor Marc Levoy's Digital Michelangelo Project. To enrich our understanding of Michelangelo's statues, we took a day-long field trip to the marble quarries and workshops of Pietrasanta. Although not as well-known as the neighboring town of Carrara, Pietrasanta is equally important in the history of sculpture. It is here that Michelangelo, working under orders from Pope Leo X, constructed a road leading to Monte Altissima, a rugged and inaccessible peak, but one known to contain rich deposits of pure white statuary marble. Cutting blocks in this wilderness and transporting them to the coast proved difficult; only the Moses and the unfinished Slaves were carved from Pietrasanta marble. In later centuries, with improvements in roadbuilding technology, quarries on Monte Altissima flourished. We will visit one of them today. By the way, you can still hike along Michelangelo's road.

The quarry

Our day begins with an early-morning drive from Florence to Pietrasanta, which lies on the western coast of Italy 30 Km north of Pisa. From here we drive into the Alpi Apuani, a side branch of the Appenine mountains that form the spine of Italy. The road is narrow and winding. Trucks rumble past us carrying 10-ton blocks of marble to sawmills on the coast.

Looking west from the road, we see a maze of ridges and canyons spilling down onto the coastal plain. Pietrasanta is roughly in the center of the photo. Carrara is out of view to the right. Pisa is to the left. Beyond is the Ligurian sea.

Our destination is a quarry of the Henraux Company. It sits on the southern shoulder of Monte Altissima, which lies out of view to the left. The altitude is 1500 meters (5000 feet), and the temperature is below freezing. This quarry is not open to the public, but our tour guide, who lived in Pietrasanta for 10 years, has obtained permission from the owners for us to visit.

This is an open-pit quarry (elsewhere marble is mined from tunnels), and in this view we see the principal working faces of the pit. The back wall (at center in the photo) is 80 meters (250 feet) high. Every surface is marble. In this quarry, the stone is lightly veined with gray - not good enough for statues, but still of high quality.

Walking into the pit, we get a better sense of its immense scale. The cavity in the middle of the back wall is 6 meters wide by 3 meters tall. The structure hugging the left wall is a staircase and workman's shed.

Moving further into the pit and looking to the right, we see that the quarriers have found a rich vein and have pursued it horizontally into the mountain. Rather than removing the overburden, they have left it in place, forming an immense corbeled (stepped) ceiling 30 meters wide by 10 meters deep.

During the Renaissance, marble was quarried by inserting wooden pegs into naturally occuring cracks in the rock, then pouring water onto the pegs to make them swell. Eventually the rock would split, liberating a piece of marble. The principal tool of modern quarrying is a wire cable 1cm in diameter, fitted at 5cm intervals with diamond-studded collars. Holes are drilled in the mountain, the cable is threaded through the holes to form a loop, and the loop is driven at high speed by an electric motor.

In this quarry the marble is extracted in rectangular blocks measuring 8' x 8' x 16'. Once the sides and back of a block have been separated from the mountain using the wire cable, the bottom is undercut from the front using a chain saw that translates along a horizontal rail.

Eventually the block splits away from the wall and topples to the ground. Marble is hard, but it is also brittle. To prevent the 80-ton block from shattering on impact, a bed of rubble is prepared beforehand. One of these blocks, newly toppled and resting on its rubble bed, is visible at the center of this picture. Too large to transport, this block will be cut into smaller blocks measuring 4' x 4' x 8' and weighing 10 tons. These will be transported by truck to a sawmill in Pietrasanta.

Once at the sawmill, blocks are sliced into slabs by a gang of parallel circular saws. The saws move slowly - 1 meter per hour. If the blocks aren't well squared, much time and marble is wasted in the sawing process. In this photo we see a graveyard of broken blocks that aren't worth the cost of trucking them down the mountain.

The marble workshops

	After driving back to Pietrasanta for a warm lunch, we visit several carving workshops. Each employs 5-10 artisans and specializes in a different product. The first one we visit specializes in copying famous statues. Their warehouse, pictured here, contains hundreds of plaster casts. These casts, sometimes made from an original statue and sometimes from other casts, may be a century old.
	In this outdoor shed, an artisan is copying Michelangelo's unfinished Dying Slave. At right is a plaster cast. (The original is in the Louvre.) At left is a partially complete marble copy. Leaning against the copy is a traditional "pointing" device. To use it, the artisan rests its wooden frame against 3 nails driven into the cast and brings its brass rod into contact with a "point" on the surface of the statue. The brass rod is then retracted into a sleeve, the frame is moved to a matching set of 3 nails on the copy, and the artisan alternately carves and advances the brass rod. When the rod reaches a premeasured depth, the artisan knows that the surface of the copy matches the surface of the cast at that point.
	Michelangelo spent 4 years carving the David. These days, a copy can be made in a few weeks or months, depending on size. Just as the wire cable revolutionized quarrying, the pneumatic chisel revolutionized marble carving. Essentially a small jackhammer, this tool not only speeds up the work but by replacing a few heavy blows with many lighter blows, it permits the carving of daring undercuts and thin protrusions. The carver in this photo employs a pneumatic chisel to execute a bas-relief based on the model at left.
	Although these artisans are highly skilled, their life is not easy. The work is dirty, physically demanding, and dangerous. In this picture, a carver roughs out a piece by scoring the edge at regular intervals with an electric disc saw and knocking off the resulting "teeth" with heavy blows of a large hammer.

A group photo of the class

Left to right: Matti Auvinen, Dana Katter, Matt Ginzton, Jeremy Ginsberg, Lucas Pereira, Amy Shultz, Joshua Schroeder, Alana Chang, Maisie Tsui, Sean Anderson, Ephraim Luft, Szymon Rusinkiewicz, and Kari Pulli. Missing: Marc Levoy (taking the picture), Unnur Gretarsdottir. Matti, a sculpture instructor from Student Art Centers International (SACI), was our tourguide for day. He also taught Professor Levoy how to carve marble. By the way, it is cold out here.

These photographs were taken with an Olympus D600L digital camera.

levoy@cs.stanford.edu

	Our day begins with an early-morning drive from Florence to Pietrasanta, which lies on the western coast of Italy 30 Km north of Pisa. From here we drive into the Alpi Apuani, a side branch of the Appenine mountains that form the spine of Italy. The road is narrow and winding. Trucks rumble past us carrying 10-ton blocks of marble to sawmills on the coast.
	Looking west from the road, we see a maze of ridges and canyons spilling down onto the coastal plain. Pietrasanta is roughly in the center of the photo. Carrara is out of view to the right. Pisa is to the left. Beyond is the Ligurian sea.
	Our destination is a quarry of the Henraux Company. It sits on the southern shoulder of Monte Altissima, which lies out of view to the left. The altitude is 1500 meters (5000 feet), and the temperature is below freezing. This quarry is not open to the public, but our tour guide, who lived in Pietrasanta for 10 years, has obtained permission from the owners for us to visit.
	This is an open-pit quarry (elsewhere marble is mined from tunnels), and in this view we see the principal working faces of the pit. The back wall (at center in the photo) is 80 meters (250 feet) high. Every surface is marble. In this quarry, the stone is lightly veined with gray - not good enough for statues, but still of high quality.
	Walking into the pit, we get a better sense of its immense scale. The cavity in the middle of the back wall is 6 meters wide by 3 meters tall. The structure hugging the left wall is a staircase and workman's shed.
	Moving further into the pit and looking to the right, we see that the quarriers have found a rich vein and have pursued it horizontally into the mountain. Rather than removing the overburden, they have left it in place, forming an immense corbeled (stepped) ceiling 30 meters wide by 10 meters deep.
	During the Renaissance, marble was quarried by inserting wooden pegs into naturally occuring cracks in the rock, then pouring water onto the pegs to make them swell. Eventually the rock would split, liberating a piece of marble. The principal tool of modern quarrying is a wire cable 1cm in diameter, fitted at 5cm intervals with diamond-studded collars. Holes are drilled in the mountain, the cable is threaded through the holes to form a loop, and the loop is driven at high speed by an electric motor.
	In this quarry the marble is extracted in rectangular blocks measuring 8' x 8' x 16'. Once the sides and back of a block have been separated from the mountain using the wire cable, the bottom is undercut from the front using a chain saw that translates along a horizontal rail.
	Eventually the block splits away from the wall and topples to the ground. Marble is hard, but it is also brittle. To prevent the 80-ton block from shattering on impact, a bed of rubble is prepared beforehand. One of these blocks, newly toppled and resting on its rubble bed, is visible at the center of this picture. Too large to transport, this block will be cut into smaller blocks measuring 4' x 4' x 8' and weighing 10 tons. These will be transported by truck to a sawmill in Pietrasanta.
	Once at the sawmill, blocks are sliced into slabs by a gang of parallel circular saws. The saws move slowly - 1 meter per hour. If the blocks aren't well squared, much time and marble is wasted in the sawing process. In this photo we see a graveyard of broken blocks that aren't worth the cost of trucking them down the mountain.