Five students at the Warren County Christian School are developing a new theory on how geodes are formed.
The students brothers Tommy and Josh Jones, siblings Marcus and Abby Root, and Sam Peachy are members of the WCCS Geology Club, which also earns them one-quarter credit scholastically.
Teacher John Lewis said, "I give them guidance in their study, but they are doing the work."
Several explanations of how geodes were formed have been more or less accepted for decades, but the theory the club is advancing is that they were all formed by volcanic activity, and the students are in the research phase for a scientific paper presenting evidence to that effect.
The club has a collection of well over 150 geodes collected by Lewis between Warren and Washington State, giving the members a good statistical base to work with. Some came from Mount St. Helens, some from the Great Salt Lake in Utah, and a good number from an area where Iowa, Missouri, and Illinois border each other. Each sample site, according to Lewis, was four feet long, 18 inches wide, and one foot deep.
The students begin their research with a physical examination, measuring the largest dimension and taking an accurate weight. They then catalogue each specimen, graphing the measurements, and studying the characteristics of the interior crystals.
Lewis explained that the geodes are mostly made up of quartz, usually a solid exterior, and the crystals that are revealed when the stone is opened provide more information. Different colors are caused by the presence of different elements, such as iron and iron compounds, manganese, calcium, and others; and the temperatures and cooling times. Geodes are commonly round and hollow, but occasionally are oval or teardrop shaped, and some are solid.
Opening them is accomplished by starting the break with a diamond saw, then finishing the cut with a hammer and chisel. Sometimes they break into more than two pieces, and Lewis said that Abby Root is the most accomplished club member in reassembling them into two pieces. Finishing the break this way shows a more natural edge than completely cutting them with the saw.
Marcus Root demonstrated a test using black light in a dark room to make more observations. He said, "Impurities in the quartz cause the crystals fluoresce or show phosphorescence."
Lewis explained that in this case, flourescence means that they glow in the presence of black light, and phosphorescence means they continue to glow after the light is turned off.
Many geodes contain calcites, which can only crystalize at very high temperatures, and blast quartz, which is a powdered quartz that does not have the six-sided crystalline facets that the mineral would normally have. That tends to support the volcanic theory.
There is much more research needed before the club can publish the paper, the students agreed.