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mining terms

Mining terminology, at the Creede Underground Mining Museum

As mentioned in my last post, I am embarking on a two-week tour of Colorado mining towns. Before I go, there are some basic mining terms that any greenhorn or tenderfoot like me should know before venturing into a mine. Many of these terms come from the Cornish miners who came to America to work when the tin mines in Cornwall played out in the 1800’s.

First, the basic parts of a mine: you always refer to a mine as if you are facing into it. The part of the mine you are working to drill, load, and blast is called the “face.” The left-side wall is the “left rib” and the right-side wall is the “right rib.” The ceiling is the “back” and the floor is the “foot.” The back is also called the “hanging wall” and the floor the “foot wall” depending on the orientation of the ore vein.

Ore body diagram

Diagram of the original ore body.

A “tunnel” is horizontal and must see daylight at both ends. If it only opens to the outside on one end, it is called an “adit.” If it doesn’t connect to the outside at all, it is a “level.” Levels are like the various floors of a building, only underground in a mine, and they provide access to the ore body. A vertical hole that connects with the surface is a “shaft.” If it is a hole that is dug down from a level or an adit, it is a “winze,” and if it is dug upward it is a “raise.” A hole dug to follow a vein horizontally away from a level or an adit is called a “drift” and to dig out a large ore body going up or down is called a “stope.”

The valuable mineral that you are trying to dig out is the “ore,” along with useless rock called “tailings.” Usually the ore is injected as a hydrothermal body along a fault or other natural zone of weakness in the rock, and the entire mineralized zone is called the “ore body” or “lode.” If it is found as a large vertical mass with branches, it is an “ore chimney” and if it is a thin line following any direction it is a “vein.” Sometimes ore is found as crystals deposited along the walls of a natural chamber. This is called a “vug.” When a vein reaches the surface, it is an “outcrop,” and when parts of the outcrop erode away and are carried down into river valleys by water, avalanches, and gravity it will pile up in still areas of the stream, such as the inner parts of meanders along with gravel. These are called “placer” deposits (pronounced “plah-cer” and not “play-cer”).

exploratory mining

Prospectors mine the placers and conduct exploratory mining

The first miners in a new mining district are prospectors, because they are looking to find, develop, and sell a good “prospect.” Typically the first discoveries are placer deposits, because they are easy to find and work using pans, rockers, and sluices. Once the placers are played out, the prospectors head upslope to find the source outcroppings, or the “Mother Lode.” Once they find evidence of ore (such as associated minerals like iron pyrite or chalcopyrite, quartz, etc.) they will “stake a claim” by pounding stakes in the corners of the land and starting to dig exploratory shafts or adits using hand tools such as picks and shovels. They will use a windlass to haul the “muck” or loose rock out of a developing shaft with a bucket. Claims have to be an allowed size (a long, thin swath of land) and registered in the county mine office to be legal. It’s good to set up with a partner so that when one of you leaves to register a claim, the other can guard it from “claim jumpers.”

Samples of the ore are taken to an “assay” office where they are analyzed chemically to see how much valuable metals are actually in the ore. If the ore is rich, or “high grade” or if the vein widens and appears to continue, the prospector will usually sell out to a mining company with the resources and capital needed to further develop the mine.

Once the mining company buys out the prospectors, it starts to build the infrastructure needed to enlarge the mine. The irregular prospector shafts and adits are enlarged and shored up with timbers. The top of a shaft is boxed in with a “collar” and an adit’s entrance is shored up and extended outward to prevent loose rock from falling into it. This becomes a “portal.” At the top of a shaft, a “headframe” or “gallows frame” is erected out of large timbers or steel with pulleys called “sheave wheels” at the top. A braided rope or cable is brought over the sheave wheel and attached to a metal cage called a “skip” which can carry men or ore buckets in and out of the shaft. The other end of the cable is brought to a “hoist,” which is an electric or diesel winch. As the skip is raised and lowered in the mine, a series of electric bell chimes are used to signal the “hoistman” how far to raise and lower the skip. A mark on the cable tells the hoistman when the skip is “on the level.”

mine expands

After a mining company buys the prospect, it expands the mine and adds infrastructure

As the mine deepens, it will usually encounter underground aquifers or water tables which become a major problem as they start to flood the lower mine shafts. The main shaft must be dug lower than the lowest level and a pump installed to remove the water. This low-lying shaft is called a “sump” and the pumps used ran on steam, diesel, electricity, or compressed air. The biggest of these were the famous Cornish pumps found in some mines.

Eventually the shafts are too deep to economically raise all ore cars, sump water, and men to the top of the shaft. A drainage and ore removal adit is sometimes dug at the bottom of the mine that will drain out the waste water and allow easy passage of ore cars out of the side of the mountain. These adits usually have a slight downward slope to the outside so the loaded ore cars can be more easily moved. Waste rock was simply dumped out of the shaft or portal and created a “tailings pile” downslope from the mine or mill.

integrated mine

Integrated mine and mill. As the mine develops, drainage adits, interior shafts, reduction mills, smelters, and other structures are built.

As the mine gets bigger, with additional levels every 100 feet and a complex set of drifts, adits, winzes, raises, interior shafts, stopes, etc. it becomes advantageous for the owners to build their own mill instead of sending their ore elsewhere for processing. A mill is built on the side of the mountain below the lowest portal. It first sorts, then pulverizes the ore into powder, then concentrates the ore mechanically or chemically. The concentrate is then shipped by rail to a smelter for final processing and purification. Sometimes the concentrated ore is heated in a retort or furnace but not separated into its final constituent metals. This combination of metals is poured into bar-shaped or cone-shaped molds and cooled, creating “dore bars” or “buttons” which contain gold, silver, and other metals.

Once the mine is exhausted of ore, or the shaft extends down below where it can be economically drained of groundwater, or the price of the final metal drops so the mine can no longer turn a profit, it is closed down (sometimes temporarily). Today, mines have to post bonds that force them to reclaim the mine and make it safe once mining has concluded. But in the old west, the mines simply shut down and left everything where it was. Tailings piles are the most obvious evidence of mining, and the rocks are often stained a yellow, orange, or reddish brown color from iron sulfides and sulfates. Rotting timbers poke from the ground, and rusted metal scraps adorn the slopes. Drainage water still seeps from adits, often contaminated with metals or other effluents. And the shafts and portals remain, too often a temptation for the unwise to explore. A few people die each year from cave ins while exploring old mines, or get killed by handling old dynamite left in mines. In some states, such as Utah, a concerted effort is underway to close all of these abandoned mines in the name of public safety but at the expense of history. Other states, such as Colorado, seem to strike a better balance between history and safety.

Mining terms B

More mining vocabulary terms. From the Creede Underground Mining Museum.

Now there are many more terms, such as how a typical miner spends his shift to drill, load, shoot, and muck the face. We’ll talk about these later as they come up on my journey. I’m amazed at how many mining terms have made it into general vocabulary, such as “big shot” [blasting out a large section of the face], “hang-up” [when ore is blasted to fall into a lower chute but gets stuck], “getting the shaft” [to buy a worthless mine], etc. For better or worse, hard-rock mining has had a big impact on our history and our culture.

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Mollie Kathleen sign

Sign for the Mollie Kathleen gold mine

Over Labor Day weekend I traveled with my family to Denver to visit my brother-in-law’s family. On the way, we stopped off at Cripple Creek, Colorado, to tour the gold mining district. I’ve been near there twice before but never took the chance to stop and visit, so this time I determined to get there no matter what. Since we left after my classes were over on Friday at 2:45 p.m., with occasional stops for food and stretching, we didn’t get into our motel until 2:30 a.m.

Mollie Kathleen mine

Mollie Kathleen gold mine

On Saturday I got up early and drove a couple of miles out of town on Highway 67 to the Mollie Kathleen gold mine. I arrived about 8:50 and the first tour was at 9:30, so I took the time to take photos around the mine site of the old equipment and original headframes. One person there told me a bear had walked through the site just ten minutes before I arrived.

Old headframe at Mollie Kathleen mine

Old Headframe at Mollie Kathleen Gold Mine

At 9:30 we donned hard hats and were loaded tightly into the double-decker man skip to travel 1000 feet down to the bottom level of the mine. Jim Smith was our tour guide, and of all the tours I’ve taken of mines around the country, this was one of the best. Not only did he explain how the equipment was used, he actually demonstrated it (it is still in working order). We saw how hydraulic drills, stope drills, muckers, bucket dumps, and other types of equipment were used by the miners. The tour lasted about an hour. I videotaped the whole thing, but wasn’t able to take many photos because we moved through the tour fast enough that I couldn’t use both cameras at once.

Mucker model

Scale model of a mucker, Cripple Creek Heritage Center

Mollie Kathleen mine tour

Jim Smith explains stoping drill, Mollie Kathleen mine tour

Jim described how miners would discover a gold vein or deposit, and shafts and crosscuts would be dug into the bottom of the deposit so that it could be stoped upward (following the deposit as it twists through the rock), standing on planks using a stoping drill that could jam and flip you off the plank at any time. Some deposits were found filling cavities called vugs, where the gold would replace the granite rock and form rich veins. The normal grade of ore assayed at about $2 of gold per ore car; some of these vug deposits, such as the one in the Cresson Mine, assayed out at over $4000 per car. Miners were paid $3 per day at that time (the same as miners in the Tintic District in Utah) and it was common for miners to “high grade,” or smuggle rich ore samples out in the false bottoms of their lunch pails.

Crosscut tunnel and ore car

Crosscut and Ore Car, Mollie Kathleen mine

Mary Catherine (Mollie Kathleen) Gortner discovered the mine in 1891 shortly after Bob Womack and Winfield Scott Stratton had discovered their gold lodes. She was visiting her son, who was prospecting in the camp, and walked up Poverty Gulch to where he was working. As she sat down to rest, her foot kicked a rock that looked like promising gold float, and she followed the rock to its source (which had already been missed by numerous miners) and memorized its location – she was too afraid of someone jumping her claim to even mark it. When the rocks she hid in her dress assayed out as rich gold ore, she returned and staked a claim as one of the few women mine owners in the district. Since then, the Mollie Kathleen has been in more-or-less continuous operation as a producing gold mine; the Lanning family that owns it now still goes in during the winter to mine out veins. They can make a small profit, with gold at over $1200 per ounce now (the main problem for the gold mines in the district isn’t the lack of gold, but the lack of a local mill to process it). But the main source of income now is from the mine tours.

Cripple Creek Colorado

Cripple Creek, Colorado from Heritage Center

After the tour I visited the Cripple Creek Heritage Center across the street and took some panoramic videos of the town, as the view was great. There were headframes on most every hill and holes everywhere where prospectors had tried and failed to find gold. At the top of the major hills was a huge continuous tailings pile from the Cripple Creek and Victor Gold Mine, a large open pit/surface mining operation that is still operating. They are concentrating the ore through leaching the tailings piles, and it is interesting to see this modern mining operation superimposed on the older, historic mines.

Next post, I’ll describe the towns of Cripple Creek and Victor and some of the mines in the area.

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