Gold mining has come a long way during the current industrial age. Historically, gold was mined via what are called “placer deposits.” Methods of placer deposit mining include panning, sluice boxing, hydraulic mining, and dredging. Placer deposits are small gold deposits found in stream beds, hence the “panning for gold” associated with prospectors in the American West. For most of human history, this was where most gold was found.
Dredging was another technique, developed during the early twentieth century. It uses huge suction machines, many of which were multiple stories tall, to excavate sediment and material. The material is sifted and sorted in water, allowing the small gold flakes to settle to the bottom where larger rocks and particulate materials remain.
Modern Placer Gold Mining
Nowadays, sluicing is more commonly used to obtain gold from placer deposits. This method obstructs water flows to create “dead zones” in the current, allowing minerals like gold to drop down into a sluicer box. On a large modern scale, screening plants known as “trommels” pre-separate boulders and other large materials, making it easier to separate out the gold.
Hard Rock Gold Mining
Recent technological improvements have created methods for mining gold out of hard rock, rather than separating it in water. This separates ores containing metals like gold from the surrounding rock. It’s done on a very large scale, and is generally practiced by large mining companies due to the high financial investment needed to construct and maintain extensive mining equipment. Geologists find the locations of pockets of gold ore in the earth, and there are several types of locations where gold is most likely to form.
It’s often found in regions like fracture zones along tectonic faults, where water and steam can circulate. There are a few different scientific models that describe how gold can form, but they all require such circulation, which helps mining companies determine where to look. In these lode deposits, the amount of gold can be as low as ten parts per million, as gold is relatively rare. Gold of this quality can’t even be molded into gold coins or other basic valuables and assets.
For the actual drilling, a machine called a “jackleg” is used, along with explosives, massive power shovels, and other machines. These are powered by compressed air, and their angle and drilling speed can be adjusted to create mine openings. The gradual removal of the gold ore creates large “rooms,” known as “stopes” or “galleries,” which can be created either from the top down, or from the bottom up. To prevent the openings from becoming unstable and caving in, scaffolding is sometimes used. Miners may also use support pillars, square sets, and other methods to keep the mines stable.
Weighing & Transport
To transport the gold from deep within the mine up to the entrance, old-fashioned railway mine cars have been replaced with diesel-powered vehicles with rubber tires. The ores are then treated extensively to remove the gold.
When it comes to the ever-important weighing process, there are a wide range of scales used for mining applications. Per the latter transport method of using rail cars, mining companies can use rail car weigh scales which come in a number of forms, such in-motion rail car scales, or static.
In addition rail-based weighing systems, weighbridges are a common form of truck scale for mining companies. Because these are often fixed to a specific weighing site, it’s not uncommon today to see miners leveraging portable scale technology, namely portable axle scales. There are also a wide range of heavy-duty scales for sale that are engineered for trucks and other forms of mining equipment.
Modern gold mining technology has advanced access to deeper gold sources located in the earth, using more powerful equipment like jacklegs and faster, powered transport systems to more effectively and efficiently extract gold ore from inside of the earth. Modern geological science has allowed lode deposits to be more accurately detected, and superior technology has allowed access to gold that, in the past, would not have been reachable.