The Water Tower was not built to be a monument for the city of Chicago, but to conceal a standpipe. The standpipe stands 138 feet tall and is 3 feet in diameter. The standpipe served to equalize the water pressure flowing in from the Pumping Station across the street. The Water Tower was built by one of Chicago's earliest architects, William W. Boyington. The original design changed many times, and in 1867, construction on the final design commenced. Located at 806 North Michigan Avenue, the unique design could be seen for miles. The building was constructed out of Joliet limestone blocks quarried in Illinois, which was a substitution for the commonly used Indiana limestone.
Joliet limestone, commonly known as Sugar Run Dolomite now, which occurs in deposits in northeastern Illinois, has been quarried near the towns of Joliet, Lemont, Kankakee, Elgin, and Aurora. The stone is a member of the Niagaran formation of Silurian age.
Limestone can be either highly calcitic or dolomitic in compostion. Indiana limestone, typically in southern Indiana, is calcitic, while Joliet limestone is dolomitic.
This dolomite is a sedimentary rock that was originally deposited as a fine grained calcite mud. From time to time, a little mud (clay and silt) from the land was added to the sediment. The mud forms the darker gray streaks and mottles in the stone. At some point, probably not long after deposition, water carried magnesium into the calcium carbonate (calcite) mud and changed it to calcium- magnesium carbonate (dolomite) by replacing some of the calcium with magnesium.
Because the crystal structure of dolomite is more compact than that of calcite, the process of replacing calcite with dolomite causes a decrease in volume and a corresponding increase in porosity in the dolomite. The process frequently obliterates the distinctive shapes and internal structure of fossils. Consequently, few, if any, animal skeletons or hard parts are visible in the dolomite, although there are traces of burrowing animals. The traces will give the rock a decorative pattern that increases its worth as a building stone.
Joliet limestone is typically composed of calcium carbonate and contains dolomite. Its color ranges from grey to white when it its freshly quarried or cut. Once subjected to weathering, the color will change to a yellish buff color due to the oxidation of iron in the stone. The yellow color of Joliet Limestone after aging is its primary distinguishing visual feature. However, limestones from Kansas, Wisconsin, and Minnesota have similar colors.
The texture and structure of limestone can vary widely, from soft, poorly consolidated stone, to hard, densely compacted stone. In the past, most limestones were chosen due to their strength characteristics. But stones from the same quarry or even from the same block cut can have different properties and weathering characteristics. So, initial selection of stone is an important factor in assuring the longevity of the building.
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1. What color is the limestone on the Water Tower?
2. Do you see any patterns in the stone from trace fossils?
Do you see any fossils or partial fossils in the limestone tower?
3. Why do you think the limestone was brought in from Joliet instead of using Indiana limestone?
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