Gallery: Architectural Geology

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(These photos are all copyright 2018 by Raymond Wiggers. For permission for one-time use, please contact me at


Chicago’s Union Stockyard Gate, an excellent example of the ornamental use of Chicagoland’s local Silurian Dolostone. This 420-Myo (million year old) sedimentary rock, still a very common sight throughout the region’s built environment, was mostly quarried in Lemont and Joliet. It hit its peak of popularity with architects before the mid-1890s. 


Silurian Dolostone in its native habitat. Here its horizontal strata are dramatically exposed in a cliff face at the northern tip of Lake Michigan, in the Garden Peninsula of Upper Michigan.


A handsome stone’s Achilles’ heel: severe exfoliation of Silurian dolostone, caused by the region’s unforgiving climate, at Chicago’s Union Stockyard Gate. 


Pronounced weathering and pitting of sculpted details in the Silurian dolostone of Chicago’s Union Stockyard Gate. More modern installations using Chicagoland’s bedrock are often better protected from the elements by a coating of chemical sealant.


Detail of glacial-till-derived, nineteenth-century brick in old city power plant of Geneva, Illinois. Note the pebbles of dolostone and chert embedded in the fired clay. While most Chicagoland brick is made from lakebed deposits of uniformly small particle size, this coarse, fruitcake texture and more variable color range provide more visual interest.  Each brick has its own geologic story to tell and is not just an anonymous building block.


Louis Sullivan’s ornate botanical designs crown the vertical elements of the terra-cotta façade of Chicago’s Gage Building. These ornaments pay tribute to Sullivan’s imaginative powers, to the skill of local terra-cotta artisans who so vividly realized them, and to the special physical and chemical properties of the clay that was the source material.


Classy faux stone:  detail of a storefront in the Hyde Park section of Chicago’s South Side. While the intricate coloration of the central section suggests the pattern of light-tinted silicate mineral crystals of granite, this panel is actually an example of the Pulsichrome terra cotta produced between the World Wars by the American Terra Cotta Corporation, based in Terra Cotta, Illinois — now part of the McHenry County town of Crystal Lake.


The Spanish Baroque comes to Illinois’ Fox River Valley: detail of the flamboyant terra-cotta entrance of St. Charles’s  Hotel Baker. This demonstrates the great technical proficiency of the artisans of the American Terra Cotta Corporation.


Oswego’s Young House, as it appeared ca. 1910. Its ground story is sheathed in locally collected river-bed or fieldstone boulders – locally known as “hardheads.” (Photo by Dwight Young; courtesy of the Little White School Museum, Oswego, Illinois)



Detail of the striking Lake Superior Brownstone exterior of Hotchkiss Hall, one example of the Richardsonian Romanesque style on the main campus of Lake Forest College. Cross bedding, excellent geologic evidence that the original sand was deposited in a flowing stream, is clearly visible in the center, irregularly shaped block. This stone, which dates from the Proterozoic Eon, is somewhere between 600 and 950 million years old, and was quarried in Wisconsin’s Apostle Islands.


Kenosha’s Southport Light – a classic use of the Milwaukee region’s Cream City Brick. The off-white color, rather similar to that of the region’s Silurian dolostone bedrock, reflects the lime-rich Wisconsin clay from which the bricks was made.


Intricate sculptural detail in in the Indiana Limestone of Louis Sullivan’s Getty Tomb in Graceland Cemetery, on Chicago’s Lincoln Park district. Note the staining of the central stone panels from the weathering of the bronze window grille above it. This is a deposit of copper (II) carbonate hydroxide caused by the bronze reacting to atmospheric water and carbon dioxide. The classic greenish-blue malachite tint is usually considered an ornamental asset of weathering bronze, but in this case it has adversely affected the stone beneath it.


The legacy of sidewalk deicers: salt-crystal efflorescence crystallizing on the otherwise impervious Indiana Limestone of Chicago’s Tribune Tower.


Cladding of the 3.5 Gyo (billion year old) Morton Gneiss (“Rainbow Granite”) on the exterior of an otherwise undistinguished bank building on Ridge Road in the historic southern suburb of Homewood. Some effort was made here to mount the panels so that the wavy foliation of this ancient metamorphic rock was oriented more or less vertically.


A chunk of attenuated dark amphibolite in a swirling halo of lighter crystals, in the façade of 333 N. Michigan Avenue. This is a fine and highly polished example of the Morton Gneiss cited in the previous caption.


Louis Sullivan’s Egyptianate Ryerson Tomb in Chicago’s Graceland Cemetery. Its exterior is clad in the uncommonly dark-toned but beautifully polished Quincy Granite of coastal Massachusetts.


The Municipal Center of St. Charles, on the bank of the Fox River, is a famous example of Art Moderne architecture. It is clad in Georgia’s gleaming Cherokee White Marble.


A beautifully preserved Jurassic-Period ammonoid fossil in a doorway of Chicago’s Pittsfield Building. This sea creature, now in a nook facing the traffic-clogged commotion of E. Washington Street, once swam in the warm waters of great Tethys Seaway.