The James River Park System - Richmond, VA

8 of 10 • start over

North Geology Tour

Stop 8b: The Wedge and Feather System

DIRECTIONS: Find rocks with square edges and chisel marks. (37.52959° N, 077.45529° W )

Digging Deeper

How could humans cut blocks of Petersburg Granite before modern machinery? With the same methods used to build the pyramids!

A quarry master studied the grain of the rock to identify a weakness along a cutting line. Holes were chiseled along this line, wedges were hammered into the holes, and the rock was eventually split.

To create a single hole it took three men; one would twist a drill as two took turns striking it with sledgehammers until the hole was 10-15 cm deep (about the length of an iPhone). Because granite is one of the hardest natural stones to cut, tools were forged of wrought iron.

wedge and feather

Granite is still sought after today for its beauty and durability, but it is harvested with carbide-tipped jackhammers and explosives.

A wedge and two “feathers” made of iron were lubricated and placed in each hole along the line. Each wedge was hammered once, moving down the line in consecutive order. The wedges had to be hammered at the same pressure for the rock to split in an even line.

Although holes were hammered in here, this piece of granite was never harvested.

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