Mine Surveying, Mine Maps, and Mine Models

Mine model used in litigation. Because of the complexity of the veins of ore in the Butte Hill, neighboring mining companies often battled in court over who had the right to exploit ore from veins deep within the hill. They hired expert geologists to testify at trial, and they often prepared models to depict in three dimensions what they believed the shape of the veins to be. This model stands in the entry to the Montana Bureau of Mines and Geology on the campus of Montana Tech. It was built by ACM for use in the Poser-Badger Suit of the 1920s. The suit was brought against ACM by several companies organized by W.A. Clark. They claimed that the discovery vein of the Rainbow lode, which apexed on the Poser mining claim, extended into ground that ACM had been mining through the Badger mine. ACM claimed that the vein it was mining was not a continuation of the vein in the Poser claim. A federal judge ruled in ACM’s favor in 1927. Source: Photo by Fred Quivik, July 2024.

When underground mining began in Butte in the 1860s and 1870s, miners followed mineral leads that they saw exposed on the surface of the Butte Hill.

The exposed, upper-most part of a vein is called the apex. Once it became apparent that veins of ore extended deep into the Earth, mining companies began to dig shafts, hoping that the shafts would strike ore. As those shafts proved successful, the mining companies drove their shafts deeper, typically in increments of 100 feet. Because Butte’s veins of ore do not sit vertically in the ground, but rather at an incline, a miner would have to work horizontally toward the anticipated vein, after driving the shaft another 100 feet deeper. That horizontal working is called a crosscut. If the crosscut struck the vein, then a mining company would drive horizontally along the vein, called drifting, to begin extracting the ore. In the early days of mining in Butte, a miner could hope that a mine working would strike ore, but he could only know for sure when the vein was exposed, and he saw it in front of his face. Each extension of a shaft downward and a crosscut horizontally was an exercise in hope, and it required the risk of capital, knowing that the hoped-for vein might not be there at a greater depth. As shafts got deeper, however, Butte mining companies and distant capitalists began to understand that beneath the Butte Hill lay a vast and rich ore body.

Butte’s veins, however, were not perfect sloping planes. They branched, they grew thicker or pinched narrower, they seemed to end only to reappear further along. This gave rise to serious litigation around the turn of the twentieth century between neighboring mining companies, as one company would begin exploiting a vein it believed was an extension of its own vein known to exist at a higher level, while a neighboring company would claim that the first company was encroaching on the second’s vein. This kind of legal conflict was called “apex” litigation. In support of the litigation, mining companies hired expert geologists and underground surveyors to try to make sense of the Butte Hill’s geological structure. Mining companies also made three-dimensional models of the veins and mine workings to enter as evidence in court. Several of these mine models are preserved and can be seen at Montana Tech and at the World Museum of Mining.

The apex litigation in Butte largely occurred in the decade before and the decade after 1900. After most of the litigation ended, because Anaconda Copper Mining Company (ACM) had consolidated ownership in 1910 of most of the mining claims on the Butte Hill, ACM began to use all the information gathered in litigation to understand the geological structure of the Butte Hill. Engineers and surveyors made maps of each level (at 100-foot intervals). Conceptually stacking those maps atop each other allowed engineers and geologists to envision the size and shape of veins in three dimensions. The underground mapping system then helped the company’s Geological Department better predict where to explore for veins of ore as the underground workings extended.