I’ve worked in the oil & gas industry in Downtown Houston for over 15 years. Like many others, every day I walk past buildings covered in lovely rocks, minerals, and fossils without a second thought. Though we may not have mountains in this part of the state, we have a stunning skyline, and I will take these beauties for granted no more! After the most recent Texas Parks and Wildlife Becoming an Outdoors Woman workshop that my friend and I teach geology for twice a year, the idea of creating a downtown walking tour sparked. We enlisted a fellow geoscientist also located in Downtown Houston to join us in our quest. We found a few scattered tours and information online (referenced below), an e-book on Amazon (link below), and little else. So Katy, Christen, and I have set out twice a week to scout all of Downtown Houston before triple digit temperatures prevent us from leaving the comfort of our air-conditioned offices.
We’ve taken hundreds of pictures and have tried to find as many facts and best guesses as possible. If you do one of our self-guided tours on your own and find more accurate information, we’d be happy to update it here. We proudly bring to you one of several self-guided walking tours: Hyatt Loop. There’s a condensed free PDF guide at the bottom of this post for easy printing or smart phone viewing. And if you need a super quick geology precursor, you can find that here: Geology Basics: For the Casual Observer or Amateur Enthusiast. Enjoy, fellow rock lovers!
WEDGE INTERNATIONAL – 1415 LOUISIANA
Building Base
Granite (dark pink, felsic-intermediate intrusive igneous)
Probably from South Dakota (very similar to Houston Public Library)
Pegmatite veins dominant
Only the base is granite, the building itself is faux
New/Accent
Granite (dark pink, felsic intrusive igneous)
Color matched: Coldspring Carnelian (trade) from Milbank, South Dakota
PreCambrian (~2 gy)
Steps
Slate (light grey, low grade metamorphic)
Maybe faux/porcelain, if so it’s well done
Pegmatite veins: holocrystalline (roughly), intrusive igneous rock composed of interlocking phaneritic crystals (usually larger than 1”)
Observed: potassium feldspar rich veins and dark mineral veins, contains both pyroxene and hornblende, uniformly parallel veins throughout
New/Accent
Some building base granite slabs have recently been replaced with more uniform medium grained granite in a slightly cooler color and with no veins (very easy to spot the difference) and contains quartz, potassium feldspar, plagioclase feldspar, and biotite
Steps
Recent (<5yrs) addition/upgrade to the building
TOTAL PLAZA – 1201 LOUISIANA
Building
Granite (grey felsic-intermediate intrusive igneous)
Color matched: Coldspring Iridian (trade) from Minnesota
PreCambrian (1.8-1.75 gy)
Fun Fact
The Petroleum Club of Houston occupies the 35th floor of the Total Plaza
Observed: uniform medium grained granite containing quartz, plagioclase feldspar, hornblende, pyroxene
1111 LOUISIANA
Building/Pavement
Diabase/ Gabbro (dark grey-black mafic intrusive igneous)
Fun Fact
In 1995, the building owners added a circle-shaped canopy that is five stories tall, which was designed by Richard Keating who was also the designer of the nearby Wells Fargo Tower
Observed: small grained but visible to naked eye, alternating polished and unpolished on building and pavement
ENTERPRISE PLAZA – 1100 LOUISIANA
Building/Pavement
Granite (pink, felsic intrusive igneous)
Spanish Rose or Rosa Porrino granite from Spain
Carboniferous (359-299my)
Pavement/Accent
Diabase/ Gabbro (dark grey-black mafic intrusive igneous)
Fun Fact
Enterprise Plaza has rose-colored windows to accompany its Spanish Pink granite exterior
Building
Medium to course grained granite with larger porphyritic/poikilitic crystals varying from thumb size to head size
Porphyritic: large microcline phenocrysts
Poikilitic texture: large component crystals contain smaller crystals of other minerals within them
Pavement/Accent
Observed: small grained but visible to naked eye, alternating polished and unpolished on fountain and pavement in arc patterns
HERITAGE PLAZA – 1111 BAGBY
Building Accent
Porphyritic Granodiorite (dark salmon intermediate intrusive igneous)
Pavement
Porphyritic Granodiorite (medium salmon intermediate intrusive igneous)
Fun Fact
The granite feature on the top of Heritage Plaza was designed to imitate a Mayan temple and was inspired by the architect’s visit to the Mexican Yucatan Peninsula
Heritage Plaza completed construction in early 1987 and was the last major office building completed in downtown Houston in the midst of the collapse of the Texas markets in the 1980’s
Building Accent
Course grained granite with larger porphyritic/poikilitic crystals
Porphyritic: large microcline phenocrysts
Poikilitic texture: large component crystals contain smaller crystals of other minerals within them
Pavement
Course grained granite with larger porphyritic/poikilitic crystals, lighter in color than on building accent but we concur that they are likely from the same or neighboring quarry
Porphyritic: large microcline phenocrysts
Poikilitic texture: large component crystals contain smaller crystals of other minerals within them
DOUBLETREE HOTEL – 400 DALLAS
Sign
Marble (dark green metamorphic, medium-grade metamorphism)
“Dirty” marble with fractures and calcite veins
Contains serpentine (green)
Valet
Marble (light green metamorphic, medium-grade metamorphism)
“Dirty” marble with fractures and calcite veins
Contains serpentine (green)
Sign
Brecciated marble: broken fragments rolled and rounded by the flow of marble under pressure
Observed: less broken fragments and more calcite veins than in valet area
Valet
Brecciated marble: broken fragments rolled and rounded by the flow of marble under pressure
Observed: more broken fragments and less calcite veins than on sign
HYATT REGENCY – 1200 LOUISIANA
Valet
Granite (brown felsic intrusive igneous)
Best guess Baltic Brown (trade) from Southern Finland (likely)
Large palm-size rounded and zoned wiborgite rapakivi poikilitic feldspar crystals
Wiborgite: orthoclase crystals that have plagioclase rims (wiborgite or viborgite type, named after the city of Vyborg)
Rapakivi: large rounded crystals of orthoclase that are surrounded by a rim of oligoclase (a variety of plagioclase)
Poikilitic texture: large component crystals contain smaller crystals of other minerals within them
BOB AND VIVIAN SMITH FOUNTAIN
Fountain
Rhyolite (pink felsic extrusive igneous)
Sign
Granite (pink felsic intrusive igneous)
Color matched: Sunset Red Granite from Texas (trade)
From Granite Mountain near Marble Falls in Texas (assumed)
PreCambrian (>1.37-1.23gy)
Could be same stone as Texas State Capitol Building in Austin
Fountain
Observed: aphanitic texture with few to no visible/distinguishable grains (any visible grains have been weathered out)
Sign
Town Mountain Granite: Coarse-grained, pink, quartz-plagioclase-microcline rock, in part porphyritic with large microcline phenocrysts. Makes up Enchanted Rock granite mass, Gillespie and Llano Counties.
Observed: contains rapakivi and poikilitic feldspars
CHEVRON – 1400 SMITH
Building Base/Pavement/Blocks
Granite/Granodiorite (grey intermediate intrusive igneous)
Color match best guess Coldspring Sierra White from Raymond, California (maybe McGilvray/Knowles?)
Early Cretaceous (111 my)
Landscaping Rocks
Sandstone (transitional sedimentary)
Moss Rock (trade), origin unknown
Fun Fact
Formerly Enron building
Building Base/Pavement
Polished base/blocks and unpolished pavement is granite (quartz 20-60% and plagioclase 10-65%) to granodiorite (quartz 20-60% and plagioclase 65-90%) with uniform medium grained crystals, weathering present
Blocks
Same or similar to building but appears newer with little to no weathering, polished
Landscaping Rocks
Moss Rock: iron rich, well sorted sandstone common as inexpensive landscaping material with weathered surface darker and richer red than fresh unweathered interior
CHEVRON FCU – 1600 SMITH
Building/Pavement
Granite/Granodiorite (grey intermediate intrusive igneous)
Color match best guess Coldspring Sierra White from Raymond, California (maybe McGilvray/Knowles?)
Early Cretaceous (111 my)
Building
Unpolished granite (quartz 20-60% and plagioclase 10-65%) to granodiorite (quartz 20-60% and plagioclase 65-90%) with uniform medium grained crystals, little to no weathering present
Pavement
Unpolished granite (quartz 20-60% and plagioclase 10-65%) to granodiorite (quartz 20-60% and plagioclase 65-90%) with uniform medium grained crystals, weathering present and concentrated around tile/block edges
KBR TOWER – 601 JEFFERSON
Building
Granite/Granodiorite (grey intermediate intrusive igneous)
Color match best guess Coldspring Sierra White from Raymond, California (maybe McGilvray/Knowles?), contains similar appearance and characteristics as Chevron complex, also unpolished
Early Cretaceous (111 my)
Download Free PDF Skyline Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Hyatt Loop) here: DowntownGeologyHyattPDF
Published Walking Tours
Skyline Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (City Hall Loop)
Tunnel Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Red Loop)
Skyline Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Hyatt Loop)
Tunnel Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Yellow Tunnel)
Skyline Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Jones Loop)
Tunnel Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Teal Tunnel)
CONTRIBUTORS
Sheila Echols-Smesny holds a Bachelor of Science in Geology from Sam Houston State University, an Executive MBA from Texas Woman’s University, and works at an oil & gas company in Houston. Red Shoes. Red Wine. is Sheila’s travel, lifestyle, & hobby blog.
Christen Peevy holds a Bachelor of Science in Geology from University of Oregon and works at an oil & gas company in Houston. Christen’s lifestyle blog is Short Sweet & Lovely.
Katy Mainwaring holds a Bachelor of Science in Geology from Texas Tech University and works at an oil & gas company in Houston. Katy teaches geology with Sheila for Texas Parks and Wildlife Becoming an Outdoors Woman program.
BEFORE YOU GO
Safety
- Look up, not at your phone, when navigating downtown
- Please be mindful of the traffic lights, pedestrian signals, bike lanes, and buses
- Buses make frequent stops and can sometimes hop curbs
- Some curbs, pavements, and streets may be uneven
Etiquette
- Please review the walking guide prior to arriving downtown to maximize time spent on the tour
- Please be mindful of downtown employees and keep slower pedestrian traffic to the right so they can go about their business
- Try to walk in pairs if walking around downtown as a group
- If approached by a homeless person, try to be firm but respectful
REFERENCES
- Houston Geological Society, 1995, Walking Tour of Downtown Houston Building Stones: Research Committee, Philip W. Porter
- Houston Gem and Mineral Society, Houston Geologic Society, 2008, Walking Tour – Houston Building Stones, Neal Immega
- United States Geological Survey: https://mrdata.usgs.gov/geology/state/map-us.html
- Brian Allison, Earth Science Guy blog (http://mnearthscienceguy.blogspot.com/2012/07/minnesota-geology-monday-granites-of-st.html)
- Wikipedia
- Geology.com
Coming soon…
Skyline Geology: A Self-Guided Walking Tour of Downtown Houston’s Buildings (Bayou Loop)
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