Geobrickology, Part 3: Close-Up of the Facade, Old St. Patrick's Catholic Church, Near West Side, Chicago, Illinois, USA (1856)
Taken at eye level, on the southern side of the church's eastern elevation.
Genuine CCB (Cream City Brick), up close and personal. The pale stone just barely visible below it is Chicagoland's own Lemont-Joliet Dolostone. It forms the building's base.
CCB, the famous product of Milwaukee's claypits, came in many different forms. If you tour the great town of its origin, you'll soon discover buildings clad in everything from aristocratic, whitish-yellow facing brick of the highest quality and durability to pebbly common brick with a palette ranging from the characteristic cream tint seen here to peach, salmon, brown, and even green, believe it or not.
But the classic color you see here, so strikingly different than that of ruddy-red and orange types made in Philadelphia, Baltimore, and St. Louis, can be traced back to the unique geochemistry of its base material.
The redness typical of most American brick is due to the oxidation of its clay's iron content when fired in the kiln. But the Cream City's clays, lacustrine and fluviatile sediments deposited in the valleys of its three major streams, are mostly derived from unusually calcium-and magnesium-rich glacial till dumped in that region by the last of the Pleistocene ice sheets. In turn, that till's composition owes much to the Silurian and Devonian dolostone bedrock of eastern Wisconsin that had been incorporated into it.
Actually, Milwaukee's clays contain as much iron as any other, but their Ca/Mg content is on average up to 15 times as great. When fired, the latter elements mask the iron-oxide color and produce white to pale yellow tones instead.
Interestingly, the brick here at Old St. Pat's appears to be a less costly, common variety—as evidenced by its pebble content (and by the pits where pebbles used to be). Most of the small surviving rock fragments have blackened. This is a common artifact of chert and other rock types long exposed to urban air pollution.
Most of the pits originally contained bits of dolostone. On firing, this carbonate rock type combusts, sometimes with a loud popping sound, into crumbly lime that soon disintegrates.
For more on this site, see my book Chicago in Stone and Clay, described at www.cornellpress.cornell.edu/book/9781501765063/chicago-i...
And the other photos and descriptions of this series can be found in my Geobrickology album.
Geobrickology, Part 3: Close-Up of the Facade, Old St. Patrick's Catholic Church, Near West Side, Chicago, Illinois, USA (1856)
Taken at eye level, on the southern side of the church's eastern elevation.
Genuine CCB (Cream City Brick), up close and personal. The pale stone just barely visible below it is Chicagoland's own Lemont-Joliet Dolostone. It forms the building's base.
CCB, the famous product of Milwaukee's claypits, came in many different forms. If you tour the great town of its origin, you'll soon discover buildings clad in everything from aristocratic, whitish-yellow facing brick of the highest quality and durability to pebbly common brick with a palette ranging from the characteristic cream tint seen here to peach, salmon, brown, and even green, believe it or not.
But the classic color you see here, so strikingly different than that of ruddy-red and orange types made in Philadelphia, Baltimore, and St. Louis, can be traced back to the unique geochemistry of its base material.
The redness typical of most American brick is due to the oxidation of its clay's iron content when fired in the kiln. But the Cream City's clays, lacustrine and fluviatile sediments deposited in the valleys of its three major streams, are mostly derived from unusually calcium-and magnesium-rich glacial till dumped in that region by the last of the Pleistocene ice sheets. In turn, that till's composition owes much to the Silurian and Devonian dolostone bedrock of eastern Wisconsin that had been incorporated into it.
Actually, Milwaukee's clays contain as much iron as any other, but their Ca/Mg content is on average up to 15 times as great. When fired, the latter elements mask the iron-oxide color and produce white to pale yellow tones instead.
Interestingly, the brick here at Old St. Pat's appears to be a less costly, common variety—as evidenced by its pebble content (and by the pits where pebbles used to be). Most of the small surviving rock fragments have blackened. This is a common artifact of chert and other rock types long exposed to urban air pollution.
Most of the pits originally contained bits of dolostone. On firing, this carbonate rock type combusts, sometimes with a loud popping sound, into crumbly lime that soon disintegrates.
For more on this site, see my book Chicago in Stone and Clay, described at www.cornellpress.cornell.edu/book/9781501765063/chicago-i...
And the other photos and descriptions of this series can be found in my Geobrickology album.