A "Chicago in Stone and Clay" Companion, Part CC-A: The Earth's Mantle Reflecting the Noonday Sun | Chicago Cultural Center (1897)
This series complements my award-winning guidebook, Chicago in Stone and Clay: A Guide to the Windy City's Architectural Geology. Henceforth I'll just call it CSC.
The CSC section and page reference for the building featured here: 5.10; pp. 53-58.
Looking at the western wall of the Grand Army of the Republic Hall.
The highly polished, sea-green and white-veined stone adorning the walls of this sumptuously ornate chamber is the Vermont Serpentinite. It's known to stone dealers and architects by the amusingly trilingual name of "Vermont Verde Antique"—to which either "Marble" or "Serpentine" is frequently suffixed.
Vermont Serpentinite is quarried in the Green Mountain State town of Rochester. The origin of this metamorphic rock type is overtly exotic: it began in the late Neoproterozoic or early Cambrian as dunite, an ultramafic igneous rock in the Earth's upper mantle beneath a now-vanished ocean basin or in a forearc zone. Then, in the succeeding Ordovician period, it was chemically altered by its contact with water, scraped up by an advancing volcanic island arc, and then thrust up onto Laurentia, the early-Paleozoic incarnation of North America.
Serpentinites and related brecciated forms called ophicalcites are quarried in various locations around the world and are prized for their rich green color and dramatic veining. While they're often best employed indoors where they will not degrade through weathering, the Vermont variety is, in my experience, more resistant in the American Midwest's challenging continental climate. Perhaps that's because its veins are mostly composed of the mineral magnesite, which is less chemically reactive than the more usual calcite.
For more on this site, get and read Chicago in Stone and Clay, described at its Cornell University Press webpage.
The other photos and discussions in this series can be found in my "Chicago in Stone and Clay" Companion album. In addition, you'll find other relevant images and descriptions in my Architectural Geology: Chicago album.
A "Chicago in Stone and Clay" Companion, Part CC-A: The Earth's Mantle Reflecting the Noonday Sun | Chicago Cultural Center (1897)
This series complements my award-winning guidebook, Chicago in Stone and Clay: A Guide to the Windy City's Architectural Geology. Henceforth I'll just call it CSC.
The CSC section and page reference for the building featured here: 5.10; pp. 53-58.
Looking at the western wall of the Grand Army of the Republic Hall.
The highly polished, sea-green and white-veined stone adorning the walls of this sumptuously ornate chamber is the Vermont Serpentinite. It's known to stone dealers and architects by the amusingly trilingual name of "Vermont Verde Antique"—to which either "Marble" or "Serpentine" is frequently suffixed.
Vermont Serpentinite is quarried in the Green Mountain State town of Rochester. The origin of this metamorphic rock type is overtly exotic: it began in the late Neoproterozoic or early Cambrian as dunite, an ultramafic igneous rock in the Earth's upper mantle beneath a now-vanished ocean basin or in a forearc zone. Then, in the succeeding Ordovician period, it was chemically altered by its contact with water, scraped up by an advancing volcanic island arc, and then thrust up onto Laurentia, the early-Paleozoic incarnation of North America.
Serpentinites and related brecciated forms called ophicalcites are quarried in various locations around the world and are prized for their rich green color and dramatic veining. While they're often best employed indoors where they will not degrade through weathering, the Vermont variety is, in my experience, more resistant in the American Midwest's challenging continental climate. Perhaps that's because its veins are mostly composed of the mineral magnesite, which is less chemically reactive than the more usual calcite.
For more on this site, get and read Chicago in Stone and Clay, described at its Cornell University Press webpage.
The other photos and discussions in this series can be found in my "Chicago in Stone and Clay" Companion album. In addition, you'll find other relevant images and descriptions in my Architectural Geology: Chicago album.