Stop T - Building Stone Walking Tour of Uptown Charlotte (sitios de interés)
Descripción del sitio
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.
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.