This is an EarthCache that will take you to a building that features the use of limestone and glass cullet. The building is on church property. However, you will not need to go onto the church property. The building and its features are observable from the street.
The Redeemer Lutheran Church Education Building was designed by Architect Bruce Goff and was completed in 1961. The walls are constructed of concrete block that is covered with a veneer of Ada limestone and studded with aqua glass cullet.
Ada limestone is a carbonate sedimentary rock from the Ada formation, which is named for the town of Ada in Pontotoc County of Oklahoma. Ada limestone is part of the Ada formation, which also includes layers of shales and sandstone. In geologic time, the Ada formation was deposited during the Ordovician period of the Paleozoic era. The Ordovician period began about 485 million years ago and lasted for about 41 million years. Limestone is one of the most durable of all natural building materials.
The glass cullet used by Goff in this building came from the Pittsburg Plate Glass plant in Henryetta, Oklahoma, which produced a glass known as “Ice Blue.” Glass cullet was a waste product of the glass manufacturing process. When the machines were shut down for maintenance or other reasons, the glass that remained was allowed to cool and harden, and was then broken up and thrown away. Glass cullet is sometimes referred to as “slag.” However, slag glass is a residue from metal smelting, where metal-rich rock (“ore”) is heated to extract the metals.
Using the glass cullet was in keeping with the teaching of the American School of design, developed under the guidance of Bruce Goff and others, which featured material resourcefulness. Subsequent to the construction of this building, modern glass manufacturing is now able to reuse the cullet by adding it to the raw materials.
The raw materials used to manufacture glass are primarily sand (silicon dioxide), limestone (calcium carbonate), and sodium carbonate. The mixture is melted in a furnace where temperatures can reach 1600° C.
In nature, volcanic glass is formed when sand and rocks, often high in silica, are heated to high temperatures, becoming molten rock, and then cooled rapidly. The temperature of the lava in volcanic tubes in Hawaiian volcanos has been recorded at about 1250° C. The molten rock cools so quickly, there is no time for crystals to grow, so the rock has a smooth, glossy shine. The main type of volcanic glass is obsidian. Obsidian is classed as an igneous rock (rather than sedimentary or metamorphic) because it is formed from magma.
How a rock breaks can help in identifying what type of mineral it is. Cleavage is a pattern of breakage along flat, even surfaces. Mica breaks into thin flat sheets, and is an example of a rock that cleaves when it breaks. In contrast to cleavage, fracture is the uneven breakage of a mineral.
Fracture patterns include conchoidal (curvy), earthy (soil-like), hackly (jagged), splintery (fibrous), and uneven (irregular).
A conchoidal fracture pattern occurs when a brittle material breaks into curvy surfaces. The term “conchoidal” derives from the resemblance of the fracture to the inside of a shell. Obsidian has a conchoidal fracture pattern. Another example of a mineral that has a conchoidal fracture pattern is quartz. A quartz crystal has a hexagonal shape but breaks with a conchoidal pattern when the break is not parallel to the crystal face.
Glass cullet and volcanic glass share some properties. Both are formed when sand and rocks are melted and then rapidly cooled. Glass cullet may be a variety of colors, depending on the minerals added in the glass-making process. Obsidian is usually black. Green obsidian is rare and found in only a few places in the world, including Oregon, in the United States, and Mexico. Aqua blue obsidian is a manmade stone.
To get credit for this EarthCache:
There is no container to find. To log this cache as a “find,” you will need to send your answer to the question below in a message. Do not post your answer in your log. You may log the find before you send your answer.
Logging Tasks
1. Answer this question: What type of fracture pattern do you observe on the glass cullet used in this building?
2. In your log, include a photograph of yourself or a personal object with the building shown in the background.
Sources
Henderson, A. (2000), “Resources Designed by Bruce Goff in Oklahoma,” NFS Form 10-900a OMB No. 1024-0018 (8-86) United States Department of the Interior National Park Service National Register of Historic Places, Section E Page 24.
Hoffner, AIA, Michael, https://www.hoffnerdesignstudio.com/blog/2019/12/13/bghenryetta
https://www.visitbartlesville.com/bruce-goffs-redeemer-lutheran-church-educational-building-bartlesville-ok-listing-58
United States Geological Survey, “Ada Group or Ada Formation,” https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=OKPAa%3B0
United States Geological Survey, “How hot is a Hawaiian volcano?” https://www.usgs.gov/faqs/how-hot-a-hawaiian-volcano
https://www.britannica.com/technology/glass
Tarbuck, E., & Lutgens, F. (2006) Earth Science, Prentice Hall, 52-53, 353.
Fay, R. (1997), Stratigraphic Units in Oklahoma, Texas, Arkansas, and Adjacent Areas, Oklahoma Geological Survey, 5.