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Posts Tagged ‘hard rock mining’

mucker

Mucker machine that runs on compressed air (Old Hundred Mine).

As my tour through Colorado’s mining towns has progressed, I’ve become much more knowledgeable about hard rock mining techniques. I created a post on basic terms of the parts of a hard rock mine and the phases of its development previously; now, it’s time to learn the terminology of the daily lives of the miners and their 12-hour shifts underground. Since these terms and techniques are common to all hard rock mines, I’ll explain them now before moving on to the second half of my day in Ouray and Telluride. That way, as I describe the specific mine tours, I’ll only have to mention those things that are unusual about each tour.

miners using a jackleg

Miners using a jackleg drill.

Each mine generally had two shifts of 12 hours each. The miner’s shift would begin by reporting to the change room, where they would put on their miner’s helmet (at first a stiffened felt hat, later a helmet with a carbide lamp) and other gear, then they would line up for the hoist to lower them down into the mine shaft in the skip, or man cage. This process would take about an hour. Different miners had different jobs; newly hired men would work the face, more experienced men would run the hoist or set up the dynamite charges and fuses, or work inside the mine as blacksmiths to keep the tools sharp.

Single jacking

Single jacking. The miner would relax his grip at the end of each swing to prevent muscle fatigue, and the jack (chisel) was rotated 1/4 each hit to prevent binding.

Old time miners would single jack the face of the ore body using a chisel and an eight-pound hammer and just one candle. Teams of two men would double jack the face: one man would hold the jack and turn it a quarter turn as the second man would hit the jack with a sledge hammer. In the darkness of just one candle, all the hammer man had to see to aim at was the single slightly reflective spot of the smashed metal at the end of the jack.

jackleg drill

Jackleg Drill (San Juan County Museum).

Eventually pneumatic drills replaced the jacks and hammers, driven by a large air compressor just off the change room at the mine’s entrance. Hoses snaked into the mine to drive the drills. Some mines used tanks of compressed air that were filled up each shift and driven on the tram into the mine. These first drills were called jacklegs because they were set up on a portable leg that could be angled into the face. Instead of a rotary motion, the drills used a hammering motion to pound into the hole. They were also called widowmakers because they put out a lot of dust that got into the miners’ lungs and caused a disease called silicosis, similar to the black lung of coal miners. The silicon dioxide dust would act like glass fragments to cause scarring in the lungs, and after a year or two of mining with a widowmaker, a miner would be “rocked up” and unable to work. They usually died within six months or so.

jackleg instructions

Diagram of how a jackleg drill works (Hard Tack Mine).

Eventually someone thought of putting a hole through the center of the drill iron and pumping water through it to mix with the dust and make a slurry. This created quite a mess to transport out of the mine, but it did control the dust and extend the miners’ lives.

Drill hole pattern

Pattern for drilling holes at the face. The center holes were left open so that the rock would fracture inward. The bottom charges went off last and lifted the rock up and out from the face.

Whether by hand or with a pneumatic drill, the miners would drill a pattern of holes in the face. Each mine used a slightly different pattern, but they all had the same purpose. Once done, dynamite was placed in each of the holes except the center one and fuses with exact lengths were attached so that when the dynamite was exploded, it would start in the first circle out from the center, which would break inward toward the empty center hole. The next ring of holes would explode a millisecond later, then the next, and finally a row of holes on the bottom would explode and lift the fractured rock up and out of the face. These shots were done at the end of a shift, so that the air would be clear when the next shift came in.

mucker instructions

Instructions for running a mucker (Hard Tack Mine).

The new shift would remove the fractured rock, a process called “mucking.” At first it was done by hand with shovels, loading the rocks into ore cars and pushing them to the hoist or out of the adit by hand. Mules were sometimes used, but it was hard hoisting them down into the shaft. They had to be trussed up to get them down, and they would stay in the mines, eventually going blind in the darkness. Electric trams were invented to replace the men and mules. Mucking machines that ran on air were also invented that would be pushed to the face on newly laid tracks, then used to scoop up the rock and lift it into an ore car behind. Another device called a slusher acted as a dragline on cables to pull ore away from the face where it could be more easily loaded. Once the rock was mucked, the miners would eat lunch, then begin drilling the holes for the next shot.

mucker diagram

Mucker operation illustration. The hopper is driven by a chain drive ran off of compressed air.

This was the round of work at the face, which was the active area of a vein going basically horizontally. When they reached the ore bodies, they would follow the ore body up and down from the horizontal levels. This process was called stoping, and it required a different type of drill, called a stoper. It was longer and designed to drill vertically upward. The ore body would be followed in all directions and a chamber would result, with sets of timber emplaced as platforms. The miners would work their way up, building more timber sets and raising the stoper higher and higher. The ore would fall down to the bottom of the stope, usually into a wooden bin with chutes from which the ore could be emptied into an ore car.

stoper diagram

How a stoper works (Hard Tack Mine).

To access the ore body, horizontal levels were blasted at 100-foot intervals down the main shaft, which then proceeded to the veins or stopes. Tunnels heading perpendicularly away from the levels were called drifts. Sometimes to get water or ore out of a mine, a long horizontal tunnel was blasted from the outside to a lower level. This was called an adit. All of these longer reaches were done with a type of drill called a drifter or a Leyner drill. It was sometimes mounted on a vertical column anchored into the rock with a long tray that moved the drill along into the face. Several of these could also be mounted on moveable platforms to lower down a shaft in order to extend the shaft deeper or they would be mounted horizontally to lengthen a level. The holes were often longer (up to 30 feet) so that more rock could be removed at a time from a single blast, and the tunnels were often larger than the drifts that accessed the ore.

leyner drill

A Leyner or drifter drill, for making deeper holes. Several of these could be attached to a platform for drilling a pattern for a drift or a shaft (San Juan County Museum).

So it would progress from shift to shift, 24 hours a day, seven days per week except holidays (Fourth of July and Christmas). Miners in remote camps would work for two week straight and get paid, then go into town for a weekend and blow it all on food, drink, gambling, and other pursuits. They would report back to work broke the next Monday.

Miners came from all over; many were from Cornwall England where they had worked in the tin mines. The Cornish tended to save up their money in order to send for their cousins and other family members to join them. These “Cousin Jacks” were hired on as soon as openings occurred at the mines. Given the prevalence of accidents and silicosis, openings were fairly frequent. The Cornish brought a number of mining terms as well as superstitions with them. The most common was the belief in Tommyknockers, small elf-like creatures that inhabited the mines and communicated with the souls of dead miners. When you heard the Tommyknockers tapping in the mine with their small hammers, it meant someone would soon die and the Cornish would refuse to go anywhere near that part of the mine. Small leftover food morsels or pieces of rich ore were left as gifts to appease the Tommyknockers.

Leyner operation

How a Leyner drill operates (Hard Tack Mine).

Those who managed to survive for several years in the mines as young men would eventually be unsuited for work inside and would have to find work topside or elsewhere (being in your mid-twenties was considered old). The daily wage of three dollars was actually considered pretty good pay back then, but eventually miners unions formed which increased the pay, provided more days off, and reduced the shift times to eight hours.

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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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