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4 Harvesting Stone

Useful stone can range in size from sand to boulders. Huge quantities of earth's stone mantle have been dislodged by various natural processes, and can be found in rivers, fields or glacier deposits. Often such free stones are appropriately sized and can be used for building as they are found. It is as if the earth has prepared these stones in advance for immediate use. Sand is also used 'as is', or at most sifted for uniformity. Some boulders are too big to use but most stones only have to be moved.

The simplest action of quarrying may be the splitting of boulders. Whether they have fallen from mountains or been left behind by receding glaciers, these boulders are not really different from the free stones gathered from fields and streams except that they are very large. The splitting of these boulders is not about dislodging, as we normally think of quarrying, but is really just processing them for use.

When free stone is not available it has to be separated from its attachment to the earth. That is when quarrying as we normally think of it begins. A quarry is an artifact of extraction. Its ultimate objective, however, is to break stone into transportable units. The need to break stone out of a matrix changes the whole game. It forces the worker into a world of ingenuity and technology. It fertilises thought.

 

A large hydraulic chainsaw is used to undercut the marble before wire saws completely dislodge the block material. Henraux marble quarry, Apennine mountains, Carrara, ItalyThe Rock of Ages granite quarry in Vermont closes down for the winter months. Barre, Vermont, USA

 

It is very likely that the first attempts to harvest intact stone were the breaking off of bits of exposed stone from stratified cliffs. Eventually, as the work continued, these sources of stone would have evolved into structured quarries[lb7] . A quarry that progressively slices off the edge of a cliff is called a bench quarry[lb8] . Repeated slicing can continue for a long time, block after block is removed as the hill or mountain is slowly shaved away. If the overborder (or overburden) becomes too extensive what began as an open quarry may turn into tunneling a second type of quarry, the cave quarry. The image most of us have of a mine is a cave quarry. A deep and dark quarry presents challenges that an open quarry does not, but it is not subject to the difficulties that weather can cause in open quarries.

Cold climate quarries can present unique difficulties. In Vermont and Sweden, the quarries temporarily shut down in the heart of winter. That precaution does not guarantee that the workers will not need to work adverse conditions. The months on either side of the break can be subject to heavy snows or bitter cold temperatures.

Even in moderately freezing weather the quarries can get slippery and workers need to have spikes on their work boots. Machinery and dump trucks need to be equipped with special chains. Daylight in northern climates is limited in winter, and curiously bright sun might not always be an advantage. Ideally there should not be sharply contrasting shadows that could lead to accidents. Deeper quarries in winter may have a very limited workday.

After temperatures reach -21ºC it is difficult to get the machines started, and below that temperature metal gets fragile. If the temperature drops after the machines are running it is possible to keep going for a while, but there is a limit. Low temperatures demand, special types of oils that do not solidify. If it is too cold, hydraulic oils for tools like drills and jackhammers must be heated because otherwise they cannot get energy and lubrication.



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