Building Stone Walking Tour of Uptown Charlotte

Stop L: Interstate Tower
121 West Trade Street

This 32 floor post-modern office building (462 feet) was finished in 1990 and designed by architects Kohn Pedersen Fox Associates PC and Odell & Associates.

L1: Serpentinite
Serpentinite is a low-grade metamorphic rock of ultramafic composition that  consists mostly of serpentine, chlorite and talc (Figure 37). It can vary in color from bright green to nearly black and is commonly referred to as “green marble” or “serpentine marble”. Serpentinites are commonly veined with calcite, dolomite, magnesite or magnesium carbonate which gives the rock its characteristic “marbled” fabric. The range in color may result from the variable amounts of forsterite and fayalite (species of olivine) that were present in the ultramafic parent rock (e.g. peridotite).

L2: Black Granite
The so-called “black granite” at the base of the building (Figure 36) is another example
of the gabbro already described for the Two Wells Fargo Plaza and the Three Wells
Fargo building (Stops G and H). This  gabbro, however, contains less labradorite than others you may have already seen.

L3: Interstate Tower light gray granite
The light gray granite (Figures 36 & 38) is felsic in nature, a term that is applied to
rocks with high feldspar and silica content. This particular granite is composed of  ~40% orthoclase feldspar (pink), ~35% plagioclase feldspar (white/gray), ~20% quartz (clear) and ~5% biotite and amphibole (black). A granite with co-crystallizing feldspars (as evidenced by their euhedral crystal shapes) is relatively unusual and is likely a result of the melt’s initial composition. Rapakivi texture (stop I), zoning, and xenoliths of a finer grained granite are also evident in this rock.

L4: Seating walls in Thomas Polk Park (Figure 39) and the columns of the four
sculptures at the corner of Trade and Tryon Streets (Figure 40) The intersection of Trade and Tryon Streets is considered the official center of the City of Charlotte and hosts four statues by artist Raymond Kasky titled “Transportation”, “Future”, “Commerce” and “Industry”. The base of the statues as well as the sculpture and walls of Thomas Polk Park which is located just in front of the Interstate Tower, are composed of a red granite with quartz veins and entrained xenoliths. A high iron content explains the deep red color. The granite used in this park is similar to that of many of the sidewalk paving stones and other features you may have noticed and have been noted throughout the tour. It is the chosen primary accent stone for the city
of Charlotte. This park marks the site of the first courthouse built by Thomas Polk, the
founder of Charlotte. The Mecklenburg Declaration of Independence was likely read here on May 20, 1775.

Stop K: SunTrust Bank (formerly First National Bank of Charlotte)
112 South Tryon Street

This 21 floor neoclassical office building (250 feet) was finished in 1926 by architect
Louis Asbury Sr.

K1: SunTrust Bank façade for floors 4-22 (look up!) The cladding for much of the SunTrust Building is an oolitic limestone quarried by the Bedford Cut Stone Company in Bedford, Indiana. The limestone is the Salem limestone,
= which a member of the Sander Group. The Salem limestone is a part of a limestone belt extending from Stinesville, in Monroe County, to Bedford, in Lawrence County, Indiana. The Salem limestone was deposited during the Middle to Late Mississippian (~335 to 340 Ma) when a shallow, inland sea covered much of the North American craton. The Salem limestone is chemically pure (~ 97% calcite) and is classified as a grainstone. It contains a variety of fossils including foraminifers, bryozoa, gastropods,
crinoids, bivalves and brachiopods. The Salem limestone is a freestone, meaning it has no preferential direction of splitting. This allows it to be cut and carved into a variety of shapes and sizes, which has made it a desirable building stone across the US since it was first quarried in 1827.

K2: Façade adjacent to the SunTrust Bank entrance
Adjacent to the SunTrust entrance is travertine (Figures 34 & 35) similar to that at stops E and O.

K3: SunTrust Bank Lower façade in the entryway
This stone is a cross-bedded sandstone whose layering is accentuated by reddish
oxidation (Figure 34). In some of the  blocks, there is evidence of wavy soft-sediment deformation. Soft-sediment deformation structures such as those visible here occur during the very first stages of sediment compaction as it begins its slow journey to becoming a sedimentary rock. The very wet and loosely packed sediments deform as they are dewatered, resulting in unusual patterns in what would have originally been relatively
simple and uniform bedding.

If you walk south along Tryon Street from the Sun Trust you might notice some nice
slates and greenish fossiliferous marbles at the entrance to the 200 S. Tryon building.

Stop J: BB&T Center
(formerly Southern National Center)
200 South College Street

A 22 floor office building (300 feet) finished in 1975 by Little & Associates architects,
this building, with its Overstreet Mall, was inspired by a Minneapolis design with the
intention of fostering retail shopping. For this reason, the building does not face a major street, but was intended to be part of an interior network of bridges between  office buildings.

J1: BB&T Overstreet Mall interior floor tiles
Head inside and upstairs into the Overstreet Mall hallway to view floor tiles that are alternating dark and light colored carbonates (Figures 31-33). Both are algal laminated (fine layering caused by the growth of agal mats) and bioturbated (mixing caused by burrowing organisms). Algal mats grow where sunlight initiates the growth of blue-green algae in shallow water, for example on the floor of a tidal flat pond. During storm events thin layers of carbonate mud can coat the algal mats. After the storm the algal mat can
re-colonize the surface. Where this process is repeated, multiple layers of algal mats can build up. The bioturbation can be recognized by the disruption of what would have been relatively flat, thinly laminated bedding.

J2: BB&T exterior cladding
The black rock that comprises much of the exterior cladding of the BB&T building
along Tryon Street is an anorthositic gabbro containing calcic plagioclase feldspar, orthopyroxene, clinopyroxene, and a small amount of amphibole. Can you recognize the weak alignment of some feldspar crystals that indicate flowing
magma?

Stop G: Two Wells Fargo Plaza
301 South Tryon

The Two Wells Fargo building (Figure 21, formerly known as Wachovia 2) features a large plaza with outdoor seating and multiple water features.  The plaza is often used for outdoor events and is a great place for a picnic lunch.  Look inside the interior lobby for more examples of marble and travertine.

G1: Exterior cladding; bench walls and capstones surrounding plaza
This visually stunning rock tells a story of several major metamorphic events (Figure 22 & 23).  The parent rock was likely a granite that was subjected to sufficiently
intense heat and pressure (amphibolite-grade metamorphism) to cause minerals of different compositions to segregate into corresponding light and dark bands clearly visible throughout the rock. This newly formed “gneiss” was then
subjected to even higher temperatures (upper granulite facies) which caused a
high level of partial melting and recrystallization of many minerals as
evidenced by the highly deformed thin bands of fine-grained mafic minerals and
regions of light-colored, mega-crystic plagioclase and orthoclase grains (light
peach and milky white in color). The final product is a migmatite. As the rock
began to cool, a third event injected molten magma into the migmatite which
crystalized into the light-colored, quartz-rich veins that cross-cut the
foliation.

G2: Fountain capstones
The dark stone benches and cladding material at the base of the Interstate Tower,
Two Wells Fargo Plaza, and in other
structures throughout the city, is often referred to as “black granite”. It actually is a gabbro containing a plagioclase feldspar known as labradorite which has a “labradoresence” or schiller effect,  consisting of a stunning play of color and blue-green iridescence visible from certain angles (Figure 24-25). This optical phenomenon is the result of light refracting within lamellar intergrowths of Na-rich and Ca-rich lamellae within the crystal  structure.  The lamellae result from phase exsolution during cooling. The medium- to coarse-grained minerals visible throughout this rock are plagioclase (grey) pyroxenes (black) and possibly some olivine (green).

G3: Plaza pavers
Light colored pavers in the plaza are a locally quarried stone, the Mount Airy Granite (described in full in stop H1).  The medium dark pavers are a granite similar
to those described at stop L4, and the dark pavers are a gabbro, both intrusive
igneous rocks formed from crystallization of magma deep within the earth’s crust.

Stop F: Charlotte Information Center
330 South Tryon

F1: Exterior planter cobbles
The river cobbles visible at the entryway to the 330 South Tryon building (Figures 17 &
18) are similar in size and roundness to typical Piedmont river cobbles. These cobbles are rounded suggesting that they have traveled a sufficient distance to have their corners smoothed. The composition of the cobbles suggests that they were eroded from a mafic source rock.

The mafic river cobbles at the 330 South Tryon building are similar in size and roundness to Pleistocene-aged quartz cobbles commonly found in terrace deposits of the nearby Catawba and Pee Dee Rivers. The cobble deposit visible in Figures 19-20 is located at a quarry adjacent to the Pee Dee River in Lilesville, NC, fifty miles southeast of uptown Charlotte. These major Piedmont rivers are typically characterized by adjacent terraces that range from a few meters to over a hundred meters in height above the modern channel and are thought to range in age from about 5000 to 1.5 million years. Gravels such as these speak to much different flow regimes in the past than those of the sand-dominated modern channels of today.

Stop I: Interior of Three Wells Fargo Center (formerly Three Wachovia Center, Three
First Union Center)
401 South Tryon Street

I1: Walls (I1 in Figure 29) contain “Calacatta Gold Marble” building stone from Italy.
This is a fine-grained, white to beige marble, formed from carbonates deposited as part of
the Lias group of the early Jurassic Period (~180 - 200 million years ago).

I2: Flooring (I2 in Figure 29) is composed of “Botachino Fiorito Marble” building stone.
This light beige, magnesian limestone is also of the Lias group of the Jurassic Period.
While this stone is called a ‘marble’ in the US and Chinese markets, in Europe it must be
called a magnesian limestone, according to the “European Standard” of building stones.

I3: Flooring (I3 in Figure 29) is composed of “Ruoms Limestone”. This dark, fossiliferous limestone is from Ruoms, a city in southern France.

I4: Flooring (I4 in Figure 29) is composed of a light-gray, coarse-grained granite building
stone known as “Luna Pearl” from either Italy or Brazil.

I5: Flooring (I5 in Figure 29) is composed of dark-colored gabbroic anorthosite. This
stone is known as “Black Galaxy Granite”. Black Galaxy is quarried near Ongole,
Andhra Pradesh, southern India. The gold specks are due to the presence of magnesium-rich orthopyroxene (“bronzite”). Black Galaxy is one of the more common stones used
throughout the US for countertops in kitchens and bathrooms.

I6: Flooring on second level.

It is worth the trip up the escalator to view the nice examples of bisectional coiled
ammonoid fossils in carbonate rocks (Figure 30). It is located in the floor tile just to the
right of the top of the up escalator.

Stop H: Exterior of Three Wells Fargo Center (formerly Three Wachovia Center, Three First Union Center)
401 South Tryon Street

This 32 floor post modern office building (450 feet) was completed in 2000. The
architects were Thompson, Ventulett, Stainback & Associates.

H1: Exterior column cladding near building, upper
The light gray, “salt-and-pepper” meta-granite (Figures 26 & 27) is from Mt. Airy, Surry County, North Carolina, (home of Andy Griffith and the town after which “Mayberry” was modeled in the well known TV series). Mississippian in age having been dated at 334 +/- 3 Ma, this light-colored, biotite granitoid or monzogranite is dominated by tabular, sodic plagioclase feldspars, many of which have their long axes parallel to a weak foliation. The Mt. Airy quarry is the largest open-faced granite quarry in the world, and is one of the few quarries in the United States that exports granite to China. Mt. Airy
Granite is the official “rock” of North Carolina.

H2: Exterior column cladding near building, lower
The pink-colored, coarse grained syenite (Figures 26 & 28) has rare quartz crystals and is dominated by pink orthoclase feldspar with some black hornblende amphibole and light colored plagioclase. The long axes of the orthoclase minerals are roughly oriented in the same direction indicating the flow of magma during crystallization. Xenoliths present in the rock appear to follow the same flow pattern. Syenites are generally formed by alkaline igneous activity, likely within thick continental crust. To produce a syenite
of this type, it is necessary to partially melt a gabbroic source rock to a relatively small
degree (~5-10%).

H3 and H4: Exterior column cladding granite
The columns near the street (Figure 26) have two additional, more “typical” garden
variety granites. There is still another one in the building cladding above the level of the
street.  Can you describe the differences?

Stop T: Hilton Charlotte Center City / One Wells Fargo Building
222 East 3rd Street

T1: Texas Pearl granite

One of the paving stones as well as the building and fountain facing stone comprises
a light pink granite known as “Texas Pearl” from Llano, Texas (Figure 74 & 75). This
Proterozoic granite is from the Town Mountain Granite suite and is comprised of albite
(white plagioclase feldspar), orthoclase (pink feldspar), quartz biotite and amphibole
(dark minerals). Here is yet another example of a rock with some Rapakivi texture.

T2: Texas Pink granite

Another one of the paving stones is a dark pink porphyritic granite known as “Texas
Pink” from Granite Shoals, Texas (Figure 76). This Proterozoic granite is also from
the Town Mountain Granite suite and is comprised of potassium feldspar (pink colored
grains), sodic plagioclase (white colored grains), quartz and biotite.

The Town Mountain Granite suite (TMG) of the Proterozoic Llano Uplift of central
Texas is generally a pink, very coarse grained, porphyritic granite with accompanying pink coarse-grained non-porphyritic granite. Mineralogically, the TMG consists primarily
of plagioclase feldspar, potassium feldspar (microcline), and quartz with biotite and/or
hornblende. Accessory minerals commonly include titanite (sphene), zircon, magnetite
and/or ilmenite, and apatite with fluorite, allanite, and/or pyrite being present in some
rocks. Texturally the granites are dominated by the large pink microcline feldspar
crystals. Differences in the color, shape, or amount of these microcline feldspar crystals
are responsible for much of the differing appearance of building stone varieties. Faint to
well-developed alignment of these large crystals (magmatic foliation) occurs somewhere in most intrusions. Regionally, the granites intrude multiply-deformed schists, gneisses,
and other metamorphic rocks of the Llano Uplift. (from http://uts.cc.utexas.edu/~rmr/
tmg.html)

Commercial quarry operations have been underway since 1882 when TMG was first
quarried to construct the Texas Capitol building.

T3: Rockville White granodiorite

A third paving stone is a light-colored phaneritic granodiorite (Figure 77) known
as “Rockville White” from Rockville, Minnesota. This Proterozoic granodiorite is a
late intrusion associated with the Penokean Orogeny (see below) and is comprised of
oligoclase (large white plagioclase feldspar), possible quartz, amphibole and biotite.

The Penokean orogeny was a major event in the formation of the North American craton.
The orogeny lasted about 10 million years and occurred in two phases. During the first
phase, the Pembine-Wausau island arc terrane collided with the ancient North American craton, along with volcanoes formed in its back-arc basin. The second phase involved a micro-continent called the Marshfield terrane, which today forms parts of Wisconsin and
Illinois.

T4: Dakota Mahogany granite

A fourth variety of paving stone at this site is a dark gray to black granite (Figure 78)
known as “Dakota Mahogany” from Milbank, South Dakota. This Archean granite is part
of the Milbank Granite Suite. It contains orthoclase feldspar, sodic plagioclase, quartz
and biotite.

Stop M: Bank of America Corporate Center
100 North Tryon Street

This 60 floor post modern office building (871 feet) finished in 1992 was designed
by Cesar Pelli & Associates Architects (Figure 41). No photos are allowed inside the building for security reasons.

M1-M3: Exterior cladding stones
Three Precambrian granites comprise the cladding stones of this building. The first is
from Ortonville, Minnesota (M1 in Figure 42) and has the trade name of “agate”. The
second is derived from Marble Falls, Texas, (M2 in Figure 42) and goes by the trade
name of “sunset beige”. The final granite (M3 in Figure 42) is from Milbank, South
Dakota and sometimes goes by the name of “carnelian” or “Dakota Mahogany” (see stop T4 for more information).

M4: Courtyard pavers
The white pavers in the BOA Corporate Center courtyard are a classic white marble
similar to the Carrara marble described in Stop D. Metamorphic black schist and a gray granite are the other two pavers.

M5: Exterior columns
The dark columns at the entryway are serpentinite, a metamorphosed peridotite (see Stop L for a full description).

M6: Fountain
The dark rock that forms the fountain is a typical medium- grained diorite that  contains fine-grained xenoliths along with pyroxene, amphibole and small amounts of quartz.

M7: Founder’s Hall flooring and walls
It is definitely worth the effort to view to the main lobby of the BOA Corporate Center
as well as Founder’s Hall, an interior shopping and dining area. The upper level of Founder’s Hall is part of the overstreet mall.

Can you identify the ~dozen different marbles utilized in the lobby of the main tower as well as in Founders Hall? These marbles came from quarries in Spain, Italy, France, Turkey and the United States. One of the pink colored Italian marbles is Devonian in age and it is known as “fior de pesco” (peach flower). It is a favorite construction material of Cesar Pelli, the building’s architect, and is especially abundant in the main hall.

Also of note, the lobby of the Bank of America Corporate Center contains one of the largest secular frescoes in the world. The fresco is the work of artist Ben Long and it took a year to complete.

Stop R: Arena Plaza
333 East Trade Street, Charlotte, NC 28202

On the plaza between the Bobcats Arena and the light rail line, there are several bench sculptures designed by Charlotte artist Paul Sires. These functional works of art feature a variety of stones from the Carolinas, Virginia, and Canada. Have a seat on rock that pre-dates the dinosaurs!

R1: Tulip bench sculpture

R1.a: Pink Kershaw Granite
The “Pink Kershaw Granite” (Figure 60), quarried in Kershaw, SC, is a classic granite, but it is technically classified as a porphyritic quartz monzonite. It is part of the Liberty Hill Pluton and is Carboniferous to Permian in age (350 to 250 million years old). Large pink crystals of perthitic orthoclase (pink colored grains) dominate this stone but albite plagioclase (white colored grains), quartz (clear to translucent minerals), hornblende and biotite (dark minerals) are also visible. Some rapakivi texture (see stop E1 for information on this texture) is visible encasing some of the orthoclase grains.

R1.b: Carolina Pink granite
The “Carolina Pink Granite” (Figure 61) is Devonian in age (415 to 355 million years)
and is derived from the Salisbury Plutonic Suite in Salisbury, North Carolina. Its
minerals include approximately 45% perthitic (characterized by linear blebs) orthoclase (pink), 25% plagioclase, 20% quartz(clear), and 10% biotite (black).

R1.c: Texas Pearl grey granite
The “Texas Pearl” grey granite (Figure 62) is a Proterozoic (2.5 billion to 550 million
years old) granite from the Town Mountain Granite Suite near Marble Falls, Texas. See stop T for more examples of granites from the Town Mountain Granite Suite and the Llano Uplift. Perthitic feldspars (pink) are present, but this rock contains more quartz than the other two rocks in the sculpture. Sodic rich plagioclase (white), amphibole and biotite (black) and quartz (gray) are also present.

R2: Half Gear bench sculpture
This bench, in the shape of half a gear (Figures 63-65), is known in the building stone trade as “Virginia Mist Granite”. This unusual rock appears to be an intermediate
igneous rock that has been  metamorphosed as shown by the flow structure (banding of light and dark minerals). It also includes unusual looking swirls of light colored plagioclase feldspar and quartz rich veins. Note the late-stage cross-cutting diabase veins (dark in color).

Overall the rock may be a Jurassic diabase quarried near Culpepper, Virginia. The
diabase is a fine- to coarsely-crystalline, sub-aphanitic to porphyritic, dark-gray mosaic of plagioclase laths (long narrow crystal habit) and clinopyroxene, with some olivine and bronzite (orthopyroxene) masses. The diabase occurs as dikes and sills associated with the Culpepper Mesozoic basin.

R3: Double Leaf bench sculpture

R3a: Crystal Gold White granite
The lighter rock in this sculpture is the “Crystal Gold White Granite” (Figure 67) and is from Vermillion Bay, in northwestern Ontario. The Nelson Granite company actively quarries syn-tectonic to pre-tectonic granites and granodiorites of the Archean Vermilion Granitic Complex. Minerals include sodium rich plagioclase feldspar (white), potassium feldspar (cream) and biotite and amphibole (black).

R3b: Forest Green granite
“Forest Green Granite” (Figure 68) is actually a gabbro from a quarry operation in Saint Sebastien de Frontenac, Quebec, Canada. The gabbro is Cambrian to Devonian in age and includes calcic-rich plagioclase (dark), pyroxene (black in the unpolished surface) and amphibole. The mineral composition and shape of the grains in this rock provide evidence that it is ‘cumulate’, meaning that most of the liquid was squeezed away during its crystallization in a magma chamber, leaving behind this assemblage of the early (high temperature) crystallizers on Bowen’s reaction series.

Stop S: Ritz Carlton Hotel
201 East Trade Street, Charlotte, NC 28202

This 17 story (200 feet) post modern building completed in 2009 was designed by Smallwood, Reynolds, Stewart, Stewart and Associates and is LEED Gold certified.

S1: Exterior upper cladding and lobby flooring
The pink and grey “marble” used in the main entrance walls and flooring in the lobby of the Ritz Carlton hotel is a fossiliferous limestone quarried in Friendsville, Tennessee, about 35 km southwest of Knoxville. How many different fossils can you find? We note at least three in this packstone to grainstone limestone: hemispherical bryozoan fragments as well as brachiopod (visible as small black arcs in Figure 70) and crinoid fragments. This pink, coarsely crystalline limestone is from the Holston Formation, a ~70-200 meter
thick stratigraphic unit within the  Chickamauga Group of the Valley and Ridge geologic province of eastern Tennessee.

The limestones of the Holston Formation formed during the Middle Ordovician (~460
million years ago) in shallow water on the southern continental shelf of Laurentia. In this environment, bryozoan-dominated reefs flourished but the high energy of the waves often broke pieces of limestone from the reef. Such fragments of bryozoans rolled across the seafloor, together with fragments of other animals, and gradually built up porous shoals of coarse-grained limestone fragments. These fossils are as coarse as ~1-2 cm in diameter and can be seen in the cut and polished surfaces of the limestone.

In the Late Ordovician, a volcanic island arc collided with the southern margin of
Laurentia causing the Taconic orogeny. Sedimentary rock strata on the continental
margin, including the Holston Formation, were pushed landward, folded, broken, stacked and buried as the Taconic Mountains rose. The pressure associated with the collision and burial compacted the limestone, and cemented the grains more firmly together.
(description from  http://academic.brooklyn.cuny.edu/geology/powell/613webpage/
NYCbuilding/TennesseeMarble/TennesseeMarble.htm)

The natural bedding in the cut limestone blocks has been used to form geometric patterns in the floor (Figure 71). This limestone can also be found in the J.P. Morgan building and Grand Central Station in New York City.

S2: Ground level exterior cladding of the Ritz Carlton hotel and unpolished pavers in the main entryway
This migmatitic (meaning the gneiss is undergoing the initial stages of melting) gneiss (provenance unknown) likely had a granitic parent body which was subjected to intense heat and pressure causing partial melting and the development of the beautiful gneissic banding that is visible. The rock appears to have been subjected to multiple subsequent metamorphic events resulting in folding of the gneissic banding.

S3: A large infilled geode in the Ritz-Carlton lobby
This large geode (Figure 73, provenance unknown) has been cut in half and polished. The stages of filling of the geode by chalcedony can be seen as layers in the polished surface. Geodes can form in any cavity (vug) within which dissolved silicates or carbonates precipitate out and form the multiple layers visible in the interior of the geode.
Can you spot the “Virginia Mist Granite” from stop R in the lobby? Can you find the
stylolites (already described in Stops D and N) in the lobby floor?
Continue to the elevator to find a stunning example of an ammonite fossil.

Stop N: Hearst Tower Interior Lobby
214 North Tryon Street

This 47 story post modern office building (659 feet) was finished in 2002 and designed by architect: Smallwood, Reynolds, Stewart, Stewart & Associates, Inc. No photos are allowed inside the building for security reasons.

Located within the College Street lobby of the Hearst Tower, there are brass railings from the Au Bon Marche department store in Paris. These railings accentuate the tower’s art deco influences. The building lacks a 13th floor for superstitious reasons.

N1-N3: Floors and walls of the interior lobby
The lighter colored floor stone is an augen gneiss (N1 in Figure 44) with the trade
name “spray white” granite. Generally, augen gneiss is a high-grade metamorphic rock whose parent rock was likely granite. Augen comes from the German word for “eye”, as the sample’s main features are lenticular porphyroblasts of white plagioclase feldspars (1 in Figure 45). Black biotite compresses around these more resistant white feldspars in a
preferred orientation. The augen gneiss was quarried at Xiamen, China, near Beijing.

The second type of stone in the flooring is “dynasty black” granite. (N2 in Figure 44)
also from Xiamen, China. This granite is a very common countertop stone, which is
actually classified as a gabbro, an igneous rock with dark minerals.

The walls in the lobby are dominated by “Beijing white” marble (N3 in Figure 44)
from Yi Sin, China. This marble has distinctive stylolites (see stop D for a definition of stylolites) which are accentuated by a coating of insoluble residue. The marble was cut as facing pieces from the same block. When one of the pieces is rotated and they are placed
side-by-side, they create a “book-end” marble effect.

Stop O: Hearst Tower courtyard
214 North Tryon Street

O1: Hearst Tower: Exterior cladding and plaza seating wall lower stone
The black walls flanking the entrance to the Hearst Tower (as well as accent seating and unpolished pavers throughout the courtyard) are composed of anorthosite (a plagioclase feldspar-dominated igneous intrusive rock) with variable plagioclase crystal sizes belonging to the Cambrian Lac-Saint-Jean anorthosite suite from Quebec, Canada. This stone (Figure 48) has the trade name of “Peirbonka granite”. In certain light, the phenocrysts (large crystals) in this rock have a lovely blue iridescence.

O2: Entry way pavers
The lighter colored pavers in the Hearst Tower courtyard is a quartz granodiorite (Figure 49) containing quartz and dominated by plagioclase feldspar (often rectangular, creamy light gray) with mafic phenocrysts (large, dark crystals in a fine-grained ground mass) of the mineral amphibole (small black crystals). Large xenoliths are present in this rock, too.
Note the well-formed plagioclase crystal laths which show evidence of compositional
zoning (growth rings) which indicate the slow cooling rates of the magma which formed this rock.

O3: Seating wall upper and unpolished paver intersections
This granodiorite (Figure 50) is weakly metamorphosed as evidenced by the subtle
alignment of elongated crystals.
Who can find the largest plagioclase xenocryst? We found one that is 10cm long!
Can you differentiate the xenocrysts from the xenoliths of other igneous rocks that were likely included as ‘hitch hikers’ as the magma from this rock intruded into the country rock?

Both the xenocrysts and xenoliths show reaction rims, halos around the crystals and rock fragments that represent partial assimilation with the magma after they were picked up.

O4: Montaldo’s Department Store (220 North Tryon) exterior cladding
The former five story Montaldo’s Department Store on the northwest corner of the Hearst Tower plaza was designed 1920 by Louis Asbury Sr. in Italian Renaissance Revival style.  The building housed the Mint Museum of Craft + Design from 1999-2010. It is clad in white travertine (Figure 51) similar to that seen at stops E and K.

Stop P: St. Peters Episcopal Church
115 West Seventh Street, Charlotte, NC 28202

St. Peter’s (Figure 52) was the first Episcopal Church in Charlotte and the parish can trace its origins to 1834. The current building at the corner of Seventh and Tryon Streets was completed in 1895.

P1: Accent stone
While much of the Church’s construction is brick, sandstone blocks (Figure 53) were
used in the foundation, doorways, stairways and windows. These sandstones are medium-grained, planar stratified, brownish red sublitharenites (mostly quartz with rock fragments). The dark red/black color visible on many of the sandstone blocks is the result of weathered iron bearing minerals and of pollution. Restoration efforts have included
plastering portions of the faces of many of the stones with stucco.

Find a stone where the stucco has chipped away in order to observe the actual color and grain characteristics of this rock.

These sandstones are likely derived from fluvial deposits found in Triassic basins (~220 million years old) in eastern North Carolina, including the Deep River Basin which underlies the Durham/Chapel Hill area. Similar sandstones were used in 19th and 20th century brownstone construction in major cities up and down the East Coast.

P2: Roof tiles
A common roofing material for this period of architecture, these slate roofing tiles
(Figure 54) are possibly derived from the Ordovician Martinsburg Formation in
Pennsylvania. Can you spot the banding in some of the tiles? This is the product of the
deposition of sediment layers prior to the metamorphism that changed the stone from shale to slate.

Stop Q: Levine Museum of the New South
200 East Seventh Street, Charlotte, NC 28202

The recently renovated museum re-opened on October 13, 2001. The museum provides a comprehensive examination of post-Civil War Southern society, history and sociological evolution for the city and region, through interactive exhibits, events, lectures and workshops.

Q1: Orange-colored exterior cladding
The cladding stone used at street level of the Levine Museum is from a limestone quarry in Lueders, Texas. The Lueders Limestone ranges from brown to gray in color and is categorized as a fine to coarse grained, bioclastic packstone (grain to grain contact with mud cement) to wackestone (grains ‘floating’ in mud matrix). The Lueders Limestone contains both fragmented body fossils (ex: shells in Figure 56) and abundant trace fossils
(Figure 57). These trace fossils record the behavior (e.g. burrowing) of organisms rather than their morphology. Trace fossils visible in this rock include planolites, a straight to gently curved horizontal burrow, as well as arthrophycus.

The Lueders Formation is the uppermost member of the Albany Group which occurs on the eastern shelf of the Midland Basin. This limestone was deposited during the Early Permian (~275.6 ± 0.7 to 270.6 ± 0.7 million years ago) when a shallow sea covered this part of West Texas.

Q2: White-colored exterior cladding
This oolitic limestone (Figure 58) was also quarried near Lueders, Texas. This limestone is a fine grained, grayish white carbonate grainstone composed of ooids (see Stop A for more information on ooids) and shell fragments, including gastropods (obvious from their elongated spiral morphology). Put your nose or a hand lens on the rock to see the small
ooids. The visible swirling pattern in some tiles is cross bedding. This bedding is due to the deposition of the carbonate particles in ripples and dunes migrating on the shallow sea floor.