Ancient Roman Mining and Quarrying Techniques

Quarrying Procedures

Figure 12: Modern touchstones, karats increasing to the right

When a vein of metals was found, a touchstone was first used to determine the quality of precious metals present. The touchstone is made of a fine-grained black siliceous rock that retains the streaks of other metals when rubbed against them. Impurities are then removed with acid treatment, and the contents of the vein are determined. This method is still used today to find how many karats are in a gold sample.

Figure 13: Active quarry site

To begin quarrying, the top layer of organic soil is removed to expose the rock face. Next, quarry men outline blocks of stone according to the size needed with iron picks and drive metal wedges in with mallets to form cracks until the stone comes loose. An alternative technique was to force dried wooden wedges wrapped in cloth into the cracks and expand them with water, forcing the stone loose.

If the quarry men were lucky, a fault line might help them by acting as one of the cracks. Stone masons had to consider both the quality of the strata and if there were any natural faults to speed up the quarrying process. From ‍‍our visit to the travertine quarry,‍‍ we learned that a straight strata with no curves indicates a strong stone while curved strata are signs of weakness. To make sure tunnels did not cave in, miners left one or more strata above them to provide enough strength. Workers also carved out stone pillars at intervals along the length of the tunnel to increase stability.

When the tuff vein pointed downward, vertical shafts were dug to continue operations. Mining would continue until the vein ended, drainage became an issue, or the effort of lifting stones from deep in the ground became too much. Immediately after loosening the stone from the quarry, the stone mason roughly shaped it to the size that was needed. It was important to leave enough excess stone so that it could be moved without damaging it, but not so much that transportation costs were too high. After removing the stone and making sure it was strong enough, it was taken to the construction site to be used.