Crushing and Sorting

Mining is simple. You drill holes into rock, you stuff explosives in those holes, and you blow the rock up into smaller pieces. From that point on everything at a mine – people, machines, buildings, and railroads – all work together to remove that rock from underground and separate any copper found within it. The first stop for the rock on this journey is the rock house.

Most rock house ruins we find offer very little clues to its original purpose. Almost all we every find – the rock bin and rail line that ran beneath it – reveals nothing of its important purpose. That was until we found the towering pillar setting atop the Mohawk #6 rock house. Here the exposed innards of a rock house were finally in view – in the form of a steam hammer pillar.

Steam hammers were just what they sounded like: steam powered hammers. These hammers were large, and were used to break apart large pieces of copper rock into more manageable pieces. You can see a steam hammer in the diagram on the left (thanks to HAER, Library of Congress) marked as #33. These were often far up in the rock house and required a concrete piling to support the machine and absorb the harsh blows they often levied. (the pier is outlined in red). While impressive, these hammers were only part of a much more involved operation; an operation that was perform hundreds of times a day in rock houses all across the Copper Country.

The Assembly Line

Rock houses were in essence vertical assembly lines, where copper rock was processed from the top of the structure to its bottom using gravity in place of a moving belt. This assembly line worked to sort the rocks coming from the mine and separate them into four separate bins representing different classifications (poor rock, copper rock, barrel copper, and mass copper). These bins would be used to load waiting railcars that would transport the rock to the stamp mill, smelter, or mine dump.

Rock coming up from the mine was loading into metal “buckets” called skips. These skips road on a set of rails and were pulled by a hoisting rope which ran from the skip, over the large wheel at the top of the rock house, and out to a distant hoist building. In the rock house these rails could be narrowed or widened, allowing the skips to dump there cargo into any one level in the rock house. What level they were dumped into, depended on what cargo they carried.

Poor Rock

The sorting of the rock leaving the mine started underground, with the trammers. These beasts of burden (men) sorted the rock by hand, and loaded it into separate skips of poor rock and copper rock. Skips containing only poor rock were dumped at a rock house’s mid level while those containing copper rock were brought further up. Most of this rock was simply dumped into a waiting bin, where rail cars hauled it off to waiting poor rock piles. Some of this material was used for construction of roads and buildings and was crushed by a crusher into smaller pieces and stored in its own bin.

Grizzlies

Skips loaded with copper rock would pass the poor rock level and head up to the top of the rock house where it was dumped. In the beginning, this rock was simply dumped onto the floor. From there men would pick through the rocks by hand to sort them for size. In the modern age (in which the Mohawk #6 rock house was in operation) this job was performed not by men, but by a grizzly.

Grizzlies were sets of parallel bars set on a slight incline. Copper rock would be dumped onto these bars, where small pieces would slip between the bars and larger pieces would not. The small pieces would fall into a waiting rock bin, while the large pieces would slide of the Grizzly and into a waiting rock crusher. Most rock houses had a series of grizzlies of varying distances between bar that worked together one on top of the other. Only the smallest rocks could pass on to the rock bin, while rocks caught up in the grizzlies would have to be processed further.

Crushing

Pieces of copper rock to large to fit through the grizzlies would need to be crushed into small pieces before finding their way into the waiting rock bin. This was done with a series of crushers. After working through the crushers the smaller pieces would be returned to the grizzly again, where the process would repeat itself until all pieces were small enough to pass through.

If a piece of copper rock was too big to fit into the crushers, they were sent to the nearby steam hammer such as the one once supported by the concrete pedestal we see at Mohawk. A few hits from this would quickly break the rock into small enough pieces to fit into the crushers.

Barrel and Mass Copper

The crushers and grizzlies could handle rock containing relatively small pieces of copper. Larger pieces of copper, such as barrel or mass copper, could be too hard to be crushed by the crushers. These would be removed from the process and handled separately.

Most copper found underground was in small pieces – in most cases nothing more then shavings. From time to time, however, larger pieces would be discovered – some as large as barrels (thus the name) or larger (called mass copper). These rocks would consist of large pieces of copper surrounded by a sprinkling of rock. Steam hammers and large drop hammers would be used to remove any adhering rock. Next theses large copper pieces would be dropped into their own rock bin or loaded directly onto rail cars using an overhead crane.

Rail Lines

The last step in the rock house process was the loading of rock cars used to deliver the various types of rocks to their next stops. For poor rock, this involved a trip by tram car over an elevated track to a nearby rock pile for dumping. For copper rock, a line of rock cars would pass under the rock house picking up rock from the overhead bin and bring it to the stamp mill some miles distant. For barrel or mass copper – too large and pure to be stamped – a separate line of rail cars would deliver it straight to the smelter or docks.

Tomorrow: Snow Walk…

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