Dakota Granite - Story of a Monument

The Story of a Monument

PART 1

The story of a monument begins with the story of Dakota Mahogany granite. According to the US Geological Service, who determines rock ages by radioactive decay, Dakota Mahogany is approximately 3.5 billion years old. In more recent times, the glacier came across the Minnesota River Valley and with tremendous force, removed the overburden from the now cooled rock, revealing outcroppings of solid granite. Being poor farm land, the outcroppings were largely ignored until 1917 when Alex Dewar, one of our founders, started to quarry it for monumental use. The granite layer in our area is said to be between 5 and 15 miles thick and its color is quite vertically consistent. In mineral makeup, Dakota Mahogany is considered a high quartz granite at about 33%. Quartz is the hardest material in our granite and is chemically similar to amethyst and other semi-precious stones. The other major component of Dakota Mahogany is a family of feldspars which are silicates and only slightly softer than the quartz. It is the feldspars which give granite its color as they contaminate with various metallic oxides. For example, aluminum oxide will tend to give the feldspars a bluish phase while iron will lend a reddish character.

In the earlier years, quarries always began with outcroppings since means of earth removal was primitive at best. In more recent times, exploration by soundings would indicate buried ledges that could be uncovered by modern earth moving equipment. Exact color of buried granite is always a guess at best. Most "discoveries" are verified by drilling off a smaller piece of the ledge and polishing it before further expenditures are made. Environmental concerns with our land have mandated reclamation plans that are costly and very time consuming to implement. This is why, in South Dakota at least, most quarriers tend to enlarge present quarries rather than to search for new deposits.

In the next part we will explore actual quarrying and the equipment and procedures necessary for the job.

PART 2

Before a monument is made, the granite for that monument has to be quarried from the earth. In the upper Northwest, granite outcroppings are the exception to the rule and efforts must be made to first locate a ledge. Dakota Mahogany only comes from a few miles of Grant County in Northeastern South Dakota, just east of Milbank. Granite is the world's most common mineral, but getting down to it can sometimes be challenging. So this issue will cover what could be called site preparation. The process of removing the earth above the ledge is called "stripping". This process reveals the boulder-like humps of solid granite that are hopefully just beneath the topsoil. Stripping will also establish the boundaries of the quarry or will modify the plan as the actual granite is located. Derrick locations will be established to serve the new workings. The derrick footings will then establish where the eight to twelve "deadmen" or anchors to the guy wires will be. They are usually built of a pile of granite blocks that will hold down a cross pin to which the guy line is attached. In some cases, the guy line can be attached to a nearby ledge. Electric power will be fed to the site and compressors will be moved in for air pressure for the drilling equipment. The new building will also house the hoists for derricks, which may be either diesel or electric. In South Dakota, heat from the compressors will help warn the hoist/compressor building in winter. Soon air and water lines will be laid to supply the men and machines.

In the Part 3, we will deal with actual quarrying of the granite.

PART 3

Last issue, we promised you that we would begin to explain quarrying procedures; however, it seems that our promise was a bit premature. We jumped ahead of the governmental issues concerning the preparation of granite quarrying.

You see, South Dakota has perhaps the most stringent mining laws in the nation. A state mining permit might seem to be a simple affair, but actually a single permit may take up to a year to complete to the state's satisfaction. A granite quarry in South Dakota is considered a surface mine to both the state and federal government.

The state requires every quarrier to have a mining permit, including a detailed reclamation plan that ensures future generations will have a safe environment. The actual procedure of filing an application includes detailed maps with elevations and drainage shown; removing of scrap material from the site; species of flora when reseeding is done; proper fencing of hazardous pits; signage for warning and many other necessary procedures. After the permit application is completed, it must be published for possible objections by environmental groups. Once the permit is acquired, the federal government will then be invited to inspect our "new" quarry. The Mining Safety & Health Administration (MSHA) is less interested in environmental concerns but are the watchdog of job safety. Dakota Granite is inspected at least four times a year. Luckily, we have never had a fatality in our quarries or shop since our beginnings in 1925.

Now can we start to quarry?

PART 4

Granite quarrying can vary in different parts of our nation, but one fact remains - it is a labor-intensive, difficult endeavor that is rarely cooperative to a quarry's wishes. We, at Dakota Granite, prefer flat floors and vertical cuts. In theory, at least, this creates cubical blocks or blocks with good "patterns" that make for minimum waste in the sawing process. A typical quarry in this area will have a yield of about 30% of total granite quarried. This fact is reflected in the large waste piles that can be seen for miles in Grant County.

After some years of drills on quarry bars and later jet burners of fuel oil and compressed air, we have returned to modern, efficient drills to create slots that are 12 feet deep around the mass to be blasted or "lifted". These slots are created by a series of adjoining vertical holes made by air drills that punch the 12-foot depth in about five minutes. A day's work with one of these machines would result in a slot that would be approximately fourteen feet long.

When the slot is completed on the back of the mass, the face of the "loaf' is attacked by a lift-hole machine that drills horizontal holes at floor level on one foot spacing into the face to stop short of entering the back slot. When that process is complete, the holes are blown out with compressed air and loaded with a sleeve of black powder and an electric cap. A typical "lift" in our Dakota Mahogany quarry might be 100' long x 40' deep and 12' high.

A blast rips the bottom of the loaf from the quarry floor just far enough to disengage the rock; but not so far as to create more fractures as the loaf falls back to the floor. A disturbance of this magnitude usually opens the natural seams in the stone which will then allow the quarrynian to work around them. The "lift" is then inspected by the quarry foremen and if the blast is considered "dean", work proceeds on a smaller scale.

PART 5

Our last installment found us in the quarry, just having made a "lift" or a blast that created a load of granite, now dislodged from the main ledge. The loaf may be 12 feet in height, about 40 feet from front to back, and as long as 140 feet. if the mass could be weighed, it would scale approximately 6700 tons!

The blast itself can be quite loud and spectacular. to say nothing of creating a lot of smoke and dust. When these things have dissipated, the quarry foreman will inspect the blast area for misfires and how the mass lifted from the ledge proper, hoping for clean and even separation. He will locate natural seams and/or new fractures. The loaf will be cleaned of debris and work we begin lining out the top of the ledge by the drilling of evenly spaced holes. This operation is done by our double-boomed, crawler drills, each capable of drilling 12-0 holes in about 6 minutes. The hole pattern will define the shape of the quarry blocks whose length will eventually be the 12-0 height of the loaf. The drill holes will act as a perforation not unlike the holes in a sheet of postage stamps.

A line of holes, however, still does not create a complete separation. When all of the holes have been drilled, the quarryman will place "wedges & shims" into each hole. The shims are actually half rounds of long steel rods between which the wedge is driven with the help of jackhammers. The resulting stress line will eventually crack the line apart and cross wedging will cut the end from the line, creating block that is now 4-6 x 4-6 x 12-0 or about 25 tons.

These steps, while sounding pretty straightforward, rarely happen without problems. Dakota Mahogany is a notoriously bad splitting stone. Drill holes must extend to the bottom of the loaf. Seams or natural fissures are rarely if ever cooperative and weather is a constant factor in a quarryman's life. Steel breaks more easily in cold weather, rubber hoses stiffen, airlines must be heated and rain and snow always come at the wrong time. In spite of these efforts, the yield on this operation is only about 30% by volume of granite quarried.

PART 6

The last installment found us with blocks coming from the quarry on their way to the next process which is sawing. in the monumental business, the pieces from which tablets and bases are made are always slabs that are typically 4", 6", 8" or 10" in, thickness. "Heavier" slabs are used as increments for slant markers or special order items such as posts. Slabbing over the years has advanced from large, reciprocating gang saws fed with steel shot, to wire saws fed with a silicon carbide slurry to the rotary diamond saw. Dakota Granite embarked on the large diamond saw concept in the early 80's as the energy crisis gave rise to higher costs of silicon carbide for wire saws. The advantages over wire saws are automation and smoother surfaces for faster polishing. One of the disadvantages over wire saws is restriction of saw height and the resulting slab widths. Wider slabs result in "layout" efficiencies. To counter this disadvantage, Dakota went for larger blade sizes. Our saw plant has five gantry type steel rails, straddling blocks to be sawn. Programming the saws for various slab thicknesses determines the travel from one cut to another. Two of our saws are capable of 1l'-6" blades, and three are designed for 14'-O blades. General Electric made a video entitled, "The Worlds, Largest Diamond Saw Blade" when our first 14'-O saw was installed in 1990. The rotating blades are tipped with 180 cobalt segments impregnated with diamonds that, when rotated against the granite blocks quickly erode the quartz and feldspar crystals. Each pass of the blade removes about 1/4" of granite resulting in a complete cut taking about 3 to 4 hours. Throughout the sawing process water is filtered and reused in a closed circuit. The blades rotate at about 130 RPM and the blade tips are replaced about every 6 weeks. Since the saws operate without human direction on weekends, a system was designed to-protect these expensive friends from harm. When trouble occurs, the saw stops; pulls out of the cut; calls a phone number and plays a tape to the absentee operator, who drives back to the plant to reset the saw! When the slabs are completely cut, they are then ready to cross the room to our polishing line, which will be our next story.

PART 7

Our last installment described the process of sawing our granite into slabs - a basic increment in the process of the making of a monument. We are now ready to polish the slabs from the sawn surface to the highly reflective surface common to most monuments. In fact, industry jargon describes the monument by the number of polished surfaces, i.e. 2, 3 or 5. Although a layman can identify quality in a polish, experts cannot tell you exactly what happens to bring a slab to polish. There are some facts that seem to prevail. The harder the stone, the easier it is to polish. High quartz granites can be highly polished. A second axiom is more difficult to understand. Granite "polish" is really not a polish at all in the sense of an additive. If anything, polishing granite is "subtractive." About four fifths of the polishing process is abrasive in nature, the first steps actually smoothing the surface toward flatness. The final process, called "buffing" glazes the surface until reflection occurs and the crystals are individually identifiable - much like a window or a cross section.

The means by which this occurs has changed over many years. Silicon carbide or aluminum oxide are two common materials in the abrasive process. Coarser abrasives are followed by finer materials until a honed surface is attained, which is best described to be nearly as dark as polish and velvet to the touch. The buffing step follows and can be done by any one of several materials. Previous to WWII, tin oxide with a slight amount of water on rotary felt buffer segments was a must. With the outbreak of the war, tin was nearly impossible to procure and less expensive materials were pressed into service. In our case, iron oxide was chosen because it was available, even though a larger quantity had to be used to achieve the same effect. Polishing was done by large machines "swinging" 36" to 52" cast iron wheels, the last of which was the buffer, stuffed with felt segments. Polishers were hired as men of strength and weight to manage the large yokes that would tend to throw lesser men around should the spinning wheel snag on an edge.

The idea that granite could be polished with abrasive bricks instead of the former "loose" abrasives was difficult for some "old timers" to grasp, and buffing to a high gloss without felt was unthinkable. in 1981, Dakota Granite purchased a 15 head, BRETON automatic slab polisher and the entire process that had required four men was reduced to one. This machine uses five-brick heads that move back and forth over the slowly moving slabs. The belt moves at a constant speed, accepting sawn slabs on one end and dispensing polished slabs on the other at the rate of 180 square feet per hour. The polish is inspected and conveyed into a specially constructed slab turner that rotates the slab so that the bottom side is up for reintroduction to the polishing line.

Our next installment will describe "layout and split" - in other words, matching order specifications to rough granite shapes.

PART 8

The last installment described the slab polishing process, which is a basic increment to the making of a monument. Our particular slabs are polished on both sides. This becomes more efficient for the "Layout" process, since a single slab can be used for dies and bases. Dakota Mahogany is not a clear granite by nature and single slabs frequently have portions that lend themselves to dies, bases and discarded granite or grout. Consequently, the gains in flexibility of layout far outweigh the extra cost of polishing both sides of the slabs.

"Layout" to us, refers to the process of dividing a slab into the required items, while maintaining a standard of grading, and doing both with maximum efficiency. Stock loss by the process - even with good stock - hovers around 40%. A partially variegated slab would increase that loss.

The layout man has the task to ordering various slabs to this table for the dies and bases he needs to make. He will outline each shape with a crayon - enlarging as necessary to "make" a final dimension. Dies and bases must match and stock decisions must be made carefully.

From the layout table, the granite is moved on a power conveyor into the splitter are where it is quickly broken to rough sizes by our Park Industries splitter. Before our first such "guillotine" in 1955, the operation was done by drilling a line of holes into which sets of steel half-rounds or "feathers" were placed, followed by the insertion of steel wedges or "pins". A sledge blow on each wedge in a sequential manner would create a stress line and the slab would eventually break - hopefully straight. Nowadays our fifth generation splitter does the same task in about four seconds from the time the tungsten carbide-tipped chisels touch the slab. With a very loud report, the granite breaks under the 600-ton pressure from the cylinders. The resulting edges are not neat enough for a finished line, but additional pitching is minimal. The usable pieces go their way toward the next process and the waste is conveyed out of the building.

The next installment will describe the process of joint sawing on dies.

PART 9

After our dies and bases are roughly sized by the splitter, the die pieces are conveyed to the joint sawing area while the base pieces go directly to our stonecutters. The edge from the splitter is not sharp enough to be considered finished. That is still a manual task performed by an individual stonecutter who recuts the line with a handset. He will also add corner lines which will define the four corners.

Margined bases will go first to a diamond saw for sawing, next to the hand polishers, back to the cutters for trimming, and only then to the craters for shipment. The die pieces, however, must first be "jointed". This seemingly simple task is a very important one, for it establishes the perpendicular and the starting point for the die. In years past, jointing was a manual task.

The stone cutter would tool the joint slightly concave in the belief that the die would stand on the edges. When the wire saws came on the scene, the joints were simply sawn. Diamond saws are now more accurate and result in a smoother surface. The speed of the diamond saw is slowed for cutting joints so as not to "rip" on the blade exit. In recent years, we have also sawn a rooftop on the tops of the dies in advance of the top grinding & polishing process that would convert that rooftop to a specified contour. A die calling for a straight top has its top sawn in addition to its joint at this point in the process. Joint sawing, while not very dramatic, is a very important process for tablets to stand straight and tall.

Our next installment will discuss top grinding and polishing.

PART 10

Our last installment was concerned with the cutting of a straight bottom or "joint" of a die or tablet. After this process, a polished 2, balance rock pitched die goes directly to the stonecutters for final shaping. But the next stop for a polished 3 (front, back & top) die is a machine that will grind and polish the contour of the top. At the turn of the century tops were hand-tooled for contour and then moved to a small, yoked polishing machine. Its small, rotating wheel was guided back and forth over the top by a very patient employee. In 1936 Dakota Granite installed a new "top machine" spinning a 24" X 12" abrasive wheel powered by a 100 HP motor. Even later, the polishing portion of the process was changed with the advent of semiautomatic polishing machines that would handle the "tedium of the tops" pretty much on their own, using a man only to replace wheels on the four steps.

In 1993 our little nest of polishers were replaced by a new Hensel System of grinding and polishing tops. The newer system is really a long track capable of accommodating a dozen dies lying on their sides. The grinding/polishing unit comes by and superimposes the desired top contour on each die. When all of the dies have been ground the unit goes back to the "home" position, changes its own wheel to a finer grit and proceeds to attend each stone on the second through seventh steps. Each die will average about 70 minutes from its sawn surface to a highly-polished, contour top. From here, the die will move to the hand polishers to blunt and repolish the edges where polish meets polish - which is our next installment!

PART 11

Our last installment had to do with polishing tops and/or ends of dies. The result of that effort will have polished tops meeting polished faces at a very sharp edge. Dakota Granite has, over the years, become famous for its "pencil polished edges" which involves the skill of what is called a hand polisher. In the face of increasing automation in granite processing the hand polisher and the stonecutter will, forever, be the holdouts. The hand polisher's tool is a hand-held, vertical-spindle air grinder spinning a wheel at about 4500 RPM. The face of that rotating wheel or pad is applied to small areas or edges in a series of ever-finer grits on the way to a polished surface.

Since a rotating grinding wheel creates dust from the wheel and the granite, they are modified to a "wet spindle." In short, the shaft is hollow and water is forced through the spindle and onto the surface of the wheel, both cooling it and reducing the dust level. Consequently, a hand-polisher wears a rubber apron to stay dry through a very wet process.

Every edge, where polish meets polish, must be blunted, rounded and then re-polished in a four-step process. A stonecutter or diamond saw may cut a margin, scotia, check or rabbet, but a hand-polisher will define the shape and make it shine. A pair of checks in the top of a die might take as long as three hours to "bring to luster."

Our next installment will describe the age-old skill of the stonecutter.

PART 12

Our last installment dealt with the task of hand polishing edges, margins and rounds. But, one of the initial and basic tasks of shaping a monument was always the stonecutter. Time was when a stonecutter was given a rough chunk and he finished the monument from shaping to lettering. As more and more of these tasks are done by various machines, his routine tasks are usually chipping or "pitching" lines on the top and ends of a tablet or on the top and bottom of bases. His basic tools are a hammer, chalk for marking, a square, and a varied assortment of chisels, hand sets, and hand points. He is also responsible for stippling, which is a texture that gives the surface a sparkle of the crystals. Stippling is done by hand and involves a tool called a 9-point or a 16-point that is used in conjunction with a pneumatic tool. "Cutters" also "clean up" rounded inside corners and create unusual members of various shapes before they are polished. When margins are called for, the stonecutter must also trim the rock below the margin.

Cornerlines, too, are a task of the stonecutters after pneumatic tool. "Cutters" also "clean up" rounded inside corners and create unusual members of various shapes before they are polished. When margins are called for, the stonecutter must also trim the rock below the margin.

Cornerlines, too, are a task the stonecutters after the top pitching is done. In an earlier installment, we described the splitter which provides the rough split bases directly to the stonecutters who will hand pitch the top and ends from the straight, but fractured edges of the split.

Polished 2 die slabs from the splitter first receive their joints and then move directly to the stonecutters for top and end pitching.

Polished 3 dies are split, jointed, tops ground and polished and then to the cutters for end pitching.

Regardless of the invention of new machines, the trade will always need the services of the stonecutter -the first and constant worker in the tooling of granite.

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