The Flickr Indianalimestone Image Generatr

Ugh this is horrible. Also it was built from 1903 to 1906, not 1904.

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In downtown Corunna, Michigan, on March 3rd, 2024, was a datestone at the Shiawassee County Courthouse (82000546 on the National Register of Historic Places; built of Bedford limestone) at the southeast corner of North Shiawassee Street (Highway M-71) and East Corunna Avenue.

Bedford limestone, a/k/a Indiana limestone, is known geologically as the Salem Limestone formation of the Sanders group, formed during the Viséan Age of the Mississippian Subperiod of the Carboniferous Period of the Paleozoic Era, ~346.7 to ~330.9 million years ago.

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Getty Thesaurus of Geographic Names terms:
• Corunna (2051605)
• Shiawassee (county) (1002892)

Art & Architecture Thesaurus terms:
• architects (300024987)
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• Indiana limestone (300011321)
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Wikidata items:
• 3 March 2024 (Q69307094)
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• Shiawassee County Courthouse (Q13409716)
• Treaty of Detroit (1807) (Q1639077)
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Library of Congress Subject Headings:
• Courthouses—Michigan (sh94008985)

I see where the designer of the 9 chose not to fully enclose its top circle, and positioned the hook of its tail unusually close to the bottom of the circle: Well, okay!

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In downtown Marinette, Wisconsin, on May 24th, 2024, was a datestone at the Stephenson Public Library (completed in 1903, designed by Patton and Hall, surfaced in Bedford limestone) at the northeast corner of Hall Avenue (U.S. Route 41) and Riverside Avenue.

Bedford limestone, a/k/a Indiana limestone, is known geologically as the Salem Limestone formation of the Sanders group, formed during the Viséan Age of the Mississippian Subperiod of the Carboniferous Period of the Paleozoic Era, ~346.7 to ~330.9 million years ago.

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Getty Thesaurus of Geographic Names terms:
• Marinette (2121739)
• Marinette (county) (2002337)

Art & Architecture Thesaurus terms:
• building stone (300011700)
• Carboniferous (300391469)
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Wikidata items:
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• Marinette County Consolidated Public Library Service (Q69495333)
• Marinette-Iron Mountain, WI-MI Combined Statistical Area (Q126131459)
• May 24 (Q2584)
• May 2024 (Q61312957)
• Mississippian (Q744718)
• Salem Limestone (Q18353656)
• Sanders Group (Q119059527)
• Stephenson Public Library (Q69866180)
• Treaty of the Cedars (Q7837316)
• U.S. Route 41 (Q12441)
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Union List of Artist Names IDs:
• Patton & Hall (American architectural firm, late 19th-early 20th century) (500516382)

September 21, 2024 - "The Pueblo Potter" by Adrian Wall stands outside the entrance to the Mesa Verde Visitor and Research Center.

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: 5.7; pp. 47-50.

Looking north-northeastward from the western side of Michigan Avenue, a little north of Monroe Street.

Just to be clear, Prudential Plaza consists of two skyscrapers, predictably named One and Two Prudential Plaza, and the thin slices of open space below them.

"One Pru," known simply known as the Prudential Building before "Two Pru" was erected, is a standard expression of 1950s Modernism, while its younger and taller sibling with the rocket-ship shape is an equally standard expression of late-twentieth-century Postmodernism. We'll focus on the latter later in this series. For now we turn our attention to One Pru.

From this distance down on Michigan, the boxy high-rise with the huge antenna seems to have an exterior of two different materials: something metallic, and a buff-colored something-or-other that might be stone. And when we go to maximum magnification of the image, we see that the buff stuff is not just on the side elevations. It also forms vertical spacers between the windows and metal spandrels of the facade.

The metal, it turns out, is aluminum, the most abundant metallic element in the Earth's crust. Nowadays it's most frequently extracted from a strange-looking ore rock called bauxite. In posts to come we'll see how the aluminum here has been crafted to provide an ornamental effect visible at closer range.

And our guess that the buff-tinted material is some type of rock is completely correct. Specifically, it's the most widely employed rock in American architecture—the Salem Limestone. This selection, quarried in southern Indiana, has been super-popular with designers ever since the Gothic Revival and Richardsonian Romanesque styles held sway in the closing decades of the nineteenth century.

Renowned for its great workability and its capacity for taking and holding fine carved detail, the Salem is a carbonate classified by sedimentary petrologists as a grainstone and biocalcarenite. In essence, these terms indicate that it's composed of particles, mostly sand-sized, which are fossil fragments of marine-organism hard parts.

As I often point out in my Stone and Clay books, given the ubiquity of the Salem in the built landscape of Chicago and Milwaukee, this rock originated when what we now call the American Midwest was largely covered by an epeiric (continent-covering) saltwater sea. This was about 345 Ma ago, during the Mississippian subperiod of the Carboniferous.

In those days, what is now the lower portion of the Hoosier State was an interface between the land and that sea. And just offshore, in the biologically abundant shallows of shoals, tidal channels, and lagoons, the broken remains of ancient creatures tossed and tumbled by currents and surf came to rest on the bottom. There they were ultimately bound together and lithified with calcite cement.

And incidentally, if you've never heard of the Salem before and thought One Pru is clad in Bedford or Indiana Limestone instead, just take a stress pill and relax. Those two monikers are the Salem's most common trade names. "Salem" itself is a reference to the rock's geologic source, classified by stratigraphers as the Salem Limestone formation.

For much more on the site touched upon here, 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.

This new 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 sections and page reference for the buildings featured here: 5.7, 5.8, 5.9; pp. 47-53.

Facing northeastward from Michigan Boulevard, a little south of Washington Street.

In CSC's introduction, I state that "to the person with the heart, soul, and understandings of a geologist, the city is not a denial of nature. It’s a vast affirmation of it." And this is true of Chicago more than any other urban center I know. This place stands proud and naked on its flat. low, and ancient lakebed, interfingered with the water, sky, and land around it. And everything in it hums with vital energy received from its surroundings.

In the photo above, advection fog formed from warm spring breezes blowing over Lake Michigan's cold surface drifts between the tops of skyscrapers of three architectural generations. In the left foreground there's the first Prudential Building ("One Pru," completed in 1954). In my childhood it was the Windy City's tallest building. Its exterior materials include Indiana's Salem Limestone, aluminum, and the rare Norwegian Støren Trondhjemite.

To its right, the Aon Center (once the Standard Oil Building, then the Amoco Building), dates to 1973. Its 83-story immensity was originally clad in Carrara Marble panels—lovely and gleaming in the light, but cut too thin. When they began to buckle and fall after prolonged exposure to the lakeshore's fearsome combination of wind, ample precipitation, and temperature extremes, they were replaced at very great cost with Mount Airy Granodiorite from North Carolina.

And poking up behind One Pru's antenna is the Postmodernist Two Pru (2 Prudential Plaza, 1990). It's primarily clad in Spanish Mondariz Granite.

All these structures, and I hope many more, will be grist for my mill in coming posts of this set. Then we'll delve deeper into this remarkable city's huge inventory of geologically derived materials.

For much more on the sites touched upon here, 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.

Looking at the base of the turret (cylindrical tower) on the hall's southwestern corner. This is just below the section depicted in Part 31 of this set.

In the previous post of this series (see link directly above) I discussed the perils of using copper fittings on stone structures. Here we see the effects of this metal's otherwise beautiful weathering chemistry: rainwater dribbling off a window sill has carried copper-carbonate and -sulfate compounds down to stain and disfigure the stone beneath.

On top of that, there are also some biofilm communities, green algae or cyanobacteria, eking out an existence not far from the copper. I would think that this metal would be toxic to them. But when it comes to those kinds of organisms, amazing tolerances and adaptations should never come as a surprise.

For some reason, architect Henry Ives Cobb elected to place a narrow base course of Salem ("Bedford," "Indiana") Limestone under the Lake Superior Brownstone (LSB) used so effectively in the rest of the exterior. It may be America's most widely used building stone, but the Salem is a lousy choice for any application where it comes into contact with the ground.

Architects of Cobb's day did not have the benefit of hindsight, and they couldn't know that this easily worked carbonate grainstone ultimately behaves very much the way LSB sandstone does—it's porous enough to wick up soil moisture and salt-laden winter meltwater. That's particularly evident where there is white salt efflorescence that has accumulated on the surface.

Careful inspection reveals that the Salem is set on top of a foundation that appears to be a coarse-aggregate concrete. It hasn't been enough, however, to keep the Salem from developing either the efflorescence cited above or some surface pitting. The long groove scored into it is also interesting. Is it the work of some passing lawn mower or power tool? The Salem is quite soft and is easily carved, intentionally or not.

Above this, the LSB, which may well be Chequamegon Sandstone from Wisconsin's Apostle Islands, is doing what it usually does, especially when it's set in improper, face-bedded fashion. One section of case-hardened rind has spalled off recently to reveal fresh stone beneath. And there are other places where the rind, still in place but quite cracked, will exfoliate before long.

Much more eye-catching, though, are the ashlar units showing deeper cavities that signal the beginning of tafoni texture. This weathering pattern of sandstones, granites, and other granular rocks involves the removal of a lot of the stone's original mass. But it does result in some lovely expositions of natural sculpture. In this image, the best example of that is the block just right of center.

If all building stones and buildings are fated to deteriorate, and they are, their turning into showplaces of tafoni's honeycombed pits and protuberances is perhaps the most artful way to go.

To see the other photos and descriptions of this series, visit
The Brownstone Chronicles album.

Looking at a small section of the building's northern elevation.

To see the church's overall aspect, take a gander at Part 32 and Part 33.

These three deeply inset, stained-glass windows almost look like arrowslits. And indeed this whole church, with its crenellated belltower, appears well designed to withstand barbarian incursions from Glencoe and Kenilworth.

This photo is, if I say so myself, a good exposition of the two carbonate rock types used again and again in Chicagoland church architecture of the late nineteenth and early twentieth centuries.

The rock that isn't an example of Regional Silurian Dolostone (RSD) is the smooth-sawn Salem Limestone of the large, downspout-like window sills. Better known in the building trades as "Bedford Limestone" and "Indiana Limestone," this Mississippian-subperiod (Lower Carboniferous) biocalcarenite and grainstone is quarried in the southern portion of the Hoosier State and is, in fact, America's most widely used building stone. It dates to about 340 Ma.

The Salem, long prized for its superb carving qualities and general workability, is (to put it diplomatically) no showboat, and in this setting is usually relegated to window trim and tracery, buttress flaps, and stringcourses. It bears an uncanny resemblance to fine-aggregate concrete, and if it does not get altered by soot deposits, it retains its bland buff to blue-gray color. Here it may have just a touch of biofilming and some salt efflorescence.

In contrast, the randomly-set Lemont-Joliet Dolostone, the RJD variety quarried in the Lower Des Plaines Valley southwest of Chicago, has a more complicated weathering palette than the Salem. On exposure to the elements and their oxidating and hydrating effects Its iron impurities weather from the ferrous (in this case bluish-gray) state to ferric ocher and rusty tints.

As noted in previous photo descriptions of this set, the Lemont-Joliet used here seems particularly flaggy and scrappy, as though it came from the lowest strata of the Sugar Run Formation, or perhaps the transition zone between the Sugar Run and the underlying Romeo Member of the Joliet Formation (ca. 425 Ma). But all that variation in size and geometry of the rock-faced stones makes for fascinating and pleasing masonry effects.

On close inspection, you'll note that some of the dolostone is quite laminated—a sedimentary feature we'll zoom in on in the photos to follow in this series.

You'll find the other photos and descriptions of this series in my Glory of Silurian Dolostone album.

Stone masons installed stone with "bagged joints"

I guess the people back then were huge fans of gray limestone? They wanted 21 stories' worth!

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In downtown Kansas City, Missouri, on March 27th, 2022, the former Federal Reserve Bank of Kansas City (built 1920-1921; designed by Graham, Anderson, Probst & White; vacated by the Federal Reserve in 2008; later known as 925 Grand; 07000327 on the National Register of Historic Places) at the northeast corner of East 10th Street and Grand Boulevard, as viewed from the southeast corner of 11th and Grand.

Per the above-linked document, the building is clad in Bedford limestone, a/k/a Indiana limestone, which is known geologically as the Salem Limestone formation of the Sanders group, formed during the Viséan age of the Mississippian subperiod of the Carboniferous period of the Paleozoic era, ~346.7 to ~330.9 million years ago.

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Getty Thesaurus of Geographic Names terms:
• Jackson (county) (2001208)
• Kansas City (7013820)

Art & Architecture Thesaurus terms:
• Carboniferous (300391469)
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Wikidata items:
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Library of Congress Subject Headings:
• Public buildings—Missouri (sh85086231)

Union List of Artist Names IDs:
• Graham, Anderson, Probst and White (American architectural firm, active ca. 1917-1937) (500211798)

The building would be easier to admire if the intrusive traffic signals were removed.

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In downtown Dallas, Texas, on February 18th, 2023, the Western Union Telegraph Company Building (built 1913-1914 at 2030 Main St; designed by Lang & Witchell; surfaced in Indiana limestone with "Egyptian"-style ornamentation; originally the Masonic Blue Lodge Temple, built for Tannehill Lodge No. 52 and Dallas Lodge No. 760; leased to Western Union starting in 1919) at the southwest corner of Main Street and South Pearl Street.

Indiana limestone, a/k/a Bedford limestone, is known geologically as the Salem Limestone formation of the Sanders group, formed during the Viséan age of the Mississippian subperiod of the Carboniferous period of the Paleozoic era, ~346.7 to ~330.9 million years ago.

The building is a "contributing property" in the Dallas Downtown Historic District, 04000894 and 08001299 on the National Register of Historic Places. The district's official documentation incorrectly says it was built in 1930.

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Getty Thesaurus of Geographic Names terms:
• Dallas (7013503)
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Art & Architecture Thesaurus terms:
• Carboniferous (300391469)
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Wikidata items:
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Union List of Artist Names IDs:
• Lang and Witchell (American architectural firm, active 1905-1938) (500230379)

Library of Congress Subject Headings:
• Buildings—Texas (sh85017805)
• Historic districts—Texas (sh95010327)