stone interiors

Mining Stone in the 19th Century

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Being composed primarily of quartz, feldspar, and mica, granite ranks at around a 7 on the Mohs scale of mineral hardness. This effectively means that it is rather difficult to scratch a piece of granite. Only a few other minerals, such as topaz and diamond, are actually capable of cutting it through. Of course, metallic tools are much more capable at drilling and cutting granite. But one can imagine the difficulties of mining granite and marble in an era where powerful and complex machinery was scarce or even nonexistent. The question emerges then, how was granite and marble mined in, say, the 19th century? As it turns out, the old practice was effectively the same as the modern day approach, but the techniques were pretty crude in comparison.

Granite is an intrusive igneous rock, meaning that it is formed by the natural cooling of molten rock underneath the surface of the Earth. Granite deposits, therefore, must be exposed by digging down into the Earth’s crust, hence the “bench” or staircase-like shape which is characteristic of open-pit mining. Explosives are used to fully expose the granite, or whichever target stone variety, from the excavated quarry. In the following account of a controlled explosion for mining stone by George Frederick Harris, a 19th century British lecturer on Economic Geology, it’s made clear that concerns for safety were minimal in the early days of the mining industry:

“Meanwhile, in those quarries where necessary, a man is sent round warning people not to come near, and sending all horses and carts out. All the quarrymen then either leave the quarries or shield themselves behind masses of the rock. A man then lights the two ends of the fuse and we, who have watched the operation run as fast as possible out of the way, hear a rumbling noise and a loud report, see hundreds of small pieces of granite fly up into the air, a crash, dense smoke, and then cautiously approaching the scene of the explosion, where the smell of powder is sometimes almost unbearable, observe the effect of the blast.”
Granites and our granite industries

From that point, blocks of granite (or marble) were often extracted using a method called "plug and feather”. In this method, a number of steel wedges are driven into the face of a segment of stone, along the lines of its grain. The wedges are braced on two sides by somewhat flattened guides, the “feathers” in “plug and feather”. After the wedges are driven, the miners wait for the stone to begin fracturing under the added pressure of each set of wedges and guides. When successful, the process is repeated until a rough block of stone could be separated from the stone face. At that point, the blocks of stone would be smoothed and cut for whatever application for which they were to be used.

Given the simplicity of the “plug and feather” procedure, it is evidenced the method was used to mine blocks of stone used in building the ancient Egyptian pyramids! In fact, while the technology of mining stone quarries has evolved, many of the same techniques, such as those described here, are still practiced to this very day. That is, without the running, screaming, and haphazard safety measures!

History · 23 July 2013