"The How's and Why's of Iron"

While it may be true that one reaps what he sows, sometimes one reaps what another plants. So it is with our generation and generations before our own as we enjoy the benefits of progress made by an earlier civilization. We are actually living in someone else's future, the future of our nineteenth century forefathers. The time we live in is the continuance of an idea started early in the 1800's, the mass production of iron and iron goods. It would later be used to make an alloy called steel which contributed to buildings of unheard of sizes. It would be used in the construction of vehicles that would travel faster and father than anyone could imagine. Even on the simple level, iron would be used to make tools stronger and more durable than ever before. None of these would have been manufactured if there weren't people who knew how to melt down the ore and pound it into useful shapes. Neither of these tasks could have been done without people to mine the ore and carry it out. And all the before mentioned steps could not have been done without someone who knew where to find the iron. Someone who knew about the geologic origins of ores, and this is what this paper is about.

I am interested in the geology of Virginia, more specifically, the Blue Ridge Mountains. The reason for this is because it was this area that supplied most of the iron ore to Buffalo Forge, the crux of our project.

The Blue Ridge mountain chain is a northeast-southwest trending range with vast ridges of varying sizes from two to fifty miles in diameter. The major feature of the Blue Ridge Mountains is the rugged rock exposures and the slopes covered with weathered rock rubble. It also has three major rivers breaching it, the Potomac, the James, and the Roanoke. All of these rivers flow towards the Atlantic and played a large part in forming the mountains. These rivers carved through the softer rocks and carry away the remains leaving the harder rocks as mountains.

"The geologic structure of the Blue Ridge involves extreme folding and faulting of very old rock terranes. Metamorphosed sedimentary and volcanic rocks overlie bedrock composed of precambrian-age metamorphosed igneous intrusions and host rocks. This package, of rocks is capped by ancient lava flows, now metamorphosized as metabasalt." Many of the rocks in this formation have been dated back to the "geologic-basement" terrane that dates back over 1.2 billion years ago. Other surrounding metamorphosed rocks are believed to be even older.¹

Copper, tin, manganese, and iron have all been mined from the Blue Ridge at one point or another. Although these are no longer being mined today, other minerals like malachite, chalcopyrite, cassiterite, turquoise, and rockbridgeite are still being extracted from the ground. Quartzite, dolostone, metabasalt, grandiorite, and unakite are being quarried along the Blue Ridge.

The reason iron is mainly found in mountains goes back the Precambrian era when much continental shifting was going on. Africa collided with North America and the land in North America began to shift inward. This led to mountains being formed over a period of thousands of years. This also explains why an older rock like one containing iron ore would be found on top of younger rock formations. In fact, the entire Blue Ridge Mountain range has been pushed far from the east to its present position.

The iron ore that was mined from the Blue Ridge Mountains was located on the west flank of the mountains in the valley. It was not, however, located on the east side of the mountains, which is odd because of the way iron is formed. As it is mentioned in the previous paragraph, iron ore was initially located on the top of the Blue Ridge Mountains. Then, due to acid rain, the iron was turned into an acidic liquid solution that flowed down both sides of the mountains. On the west flank of the Blue Ridge there is a lot of basic limestone. When the acidic iron solution hit this, it solidified making the iron ore. There was no limestone on the east side of the mountains, so it never converted to the iron ore form.

The other main factor in rock formations is weathering. Acidic rain and the before mentioned rivers ate away at several mile long chuncks of rock. The softer rocks dissolved leaving harder rocks as mountains. Sometimes we find softer rock in layers underneath harder rock and one may wonder why the softer rock was not eaten by the acidic rain or washed away by the rivers. The answer is that the stronger rock acted as a shield to the weaker mineral allowing it to surrvive beneath it.

The oldest rocks in Virginia are multi-metamorphosed rocks formed from sedimentary and igneous rocks more than 1.2 billion years ago. About 760 to 570 million years ago, multiple lava flows covered much of the area as the continents spread apart. Over the next 325 million years, broad platforms, island arcs and linear trough-like depressions formed in the area of what was to become Virginia. During the Middle Cambrian period, thick accumulations of limestone and dolostone formed on the slowly sinking platforms, and sedimentary deposits filled the troughs. About 250 million years ago North America and Africa collided which folded, uplifted, and faulted these sedimenary layers and formed the Appalachian Mountains. From that time until now, erosion has been the dominant process affecting these mountains.¹

The term ' iron ore' simply refers to any rock that contains iron. This element is usually found mixed with other minerals such as granite, shale, and limestone. Iron ore appears in Virginia in four main forms. Magnetite, the richest of the four, is a black mineral not that common in this state. Limonite, which is a brown colored ore, containes only about sixty percent iron. Siderite, the least pure of the four, contains less than fifty percent iron. Hematite, the last of the types in Virginia, was the main type of iron ore that was mined in the Blue Ridge region.²

Hematite iron ore was first mined in Virginia in 1880, and continued to be extracted for about fifty years thereafter. It is found in beds with lower Cambrian shales and quartzites. The hematite is dense and a deep bluish-green color down deep, but on the surface it weathers to a deep red. It is only second to magnetite in quality, and that by the slightest margin. Although hematite averages around seventy percent iron, this ore is not always the best for mining. It can be siliceous and low grade and in some regions it can even average between thirty-five to forty percent silica. Nevertheless, hematite yields ninety-four percent of the iron ore mined in the United States and has been the mainstay of the iron industry.^2&3

Many people have depended on the geology of the land around them for their livelihood. One great example of this is William Weaver, the iron giant of the south during antebellum times. It was the geology of the Blue Ridge Mountains that made it possible for William Weaver to make his fortune. The iron was close by and there were local rivers to run his furnaces.

On a larger scale, it was geology and the availability of iron ore that helped move this nation forward and triggered new ideas and inventions. It was because of iron that things imagined became reality. It was because of iron that we live the way we do. And none of this would have been possible without knowledge of the geological origins of ores.