Blog

By Rick Lightburn, Class of 2008

We’ve all said it a hundred times—something/someone is solid as a rock. Before there was glass and steel, rock, or stone, was used to construct buildings. And it was used to create decorative elements on buildings as well. This article presents some information about stone, adding to the thousands of details you already know about design and construction. Including some of this information could enliven the interpretation of buildings on CAC’s popular tours.

Geologists, architects, and designers can use quite different names for the same stone. While architects might specify a material they call “black granite”, a geologist will tell you that the granite might be dark grey in color, but it is never black. Geologists know that granite contains between 30% and 60% quartz. As quartz is never black, there can be no such thing as black granite. Nevertheless, remodelers will be happy to sell and install a black granite countertop for you. A geologist will look at that countertop and call it gabbro or basalt because the geologic processes that produce granite, basalt, and gabbro are very similar. These three have fairly similar physical properties that can result in understandable confusion.

A handsome example of stonework that looks black and looks like granite is on the Field Building at the northeast corner of Adams and LaSalle.

The stone of the original hotel lobby in the Auditorium Building, now the lobby of Roosevelt University, is gorgeous. It looks like it might have been alive, which may be why Louis Sullivan chose it. Decorators, designers, and rock hounds will offer the name “Mexican onyx”. It is the same stone used to make many charming trinkets that can be picked up at Mexican markets. While “Mexican onyx” is indeed Mexican, it isn’t onyx. It is also known as “onyx marble”, but geologists know it is neither marble or onyx. This handsome stone can be seen on the Historic Skyscrapers tour.

Many old buildings in Chicago are constructed of a honey-colored stone with an uneven texture: Holy Name Cathedral on State Street, the Union Park Congregational Church on Ashland Avenue, the Water Tower on Michigan Avenue, many townhouses like those on Maypole Street east of Garfield Park, and commercial buildings on Grand, Halstead, Archer, and Roosevelt Avenues (I like this stone, and I keep a list of buildings where it is used).

Called dolomite, it comes from quarries located between Joliet and Lemont that closed around 1930. It was a dominant material for buildings in Chicago between 1845 and 1880. About 1880, Indiana limestone, a gray and more uniform stone, became commercially available. Dolomite is related to limestone but is chemically different. It can be used like limestone and worked with the same tools and techniques. Its use to create lintels and sills on brick structures of the era suggests a way of dating those buildings: structures made of Indiana limestone are from a later date. Joliet-Lemont dolomite can easily be quarried into large sheets only few inches thick but twenty feet or more wide. These thin sheets could be used as the façade or a floor.

When this material was introduced to the building trades in the first part of the 19th century, it was called Athens Marble. This seems to me to be so presumptuous a name that I think of it as a stretcher. It isn’t marble and it isn’t from Athens.

Stone is a wonderful building material, and the stories of the stone can be a part of what we say to our guests. That is, if we can get the names straight!