I Like my Eggs Hard Boiled
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This earth cache brings you to an area that, if you are mining, you must sign in at the main office before you proceed. Most areas require only an average vehicle, although some of the remote areas require a 4X4.
Thunder eggs are the official rock of Oregon, although they can be found across the world and are unique to volcanic areas. According to the native legends of the Pacific Northwest, the Thunder spirits who lived in the highest Mountains such as Mt Jefferson and Mt Hood would hurl these rocks at each other when they became angry.
The particular area in which this earth cache is located has been created primarily by more events that are recent in geologic history. Over time in the high desert region of the Redmond-Bend area, shield volcanoes have laid a thick foundational flow of basalt and rhyolite. The newer strato-volcanoes have set an andesite layer that can be seen sitting on top of the older layers due to extensive erosion by flooding and cutting of the area rivers such as the Deschutes and the Crooked River. The thunder egg treasures are to be found in the older sediments laid by the shield volcanoes such as Pilot Butte (in Bend), Mt Defiance, and Underwood Mountain.
Although geodes and agates are often used synonymously with thunder eggs, they are not necessarily the same thing. Geodes will always have a specific hollow inside that often includes crystalline growths. Thunder eggs have a specific growth pattern that differentiates them. In other words, a geode can be an thunder egg, but not all thunder eggs are geodes.
When a thunder egg is sliced open, the intricate patterns and colours will vary greatly from stone to stone. The excitement to geologists and rock hounds alike is to discover these patterns; which will never be the same in any one rock. Thunder eggs may contain any type of structure within, from agate to quartz to amethyst to opals. Anyone can purchase these rocks throughout Oregon – the purpose of this Earth Cache is to provide a hands on, close-up experience of these wonderful and unique formations.
Other minerals occurring in thunder eggs can include jasper, calcite, aragonite, zeolite, and dendrite. The exact formation and crystal layerings are dependent on the particular ecology of their specific area. In the area of this earth cache, the primary mineral formations include agate, opal, red moss agate, blue agate and even rare formations such as fire opal and Priday Plume.
According to current geologic understanding, thunder eggs are formed when air pockets in the hardened rhyolite layers of a volcanic flow fill with water. This water is rich in area minerals such as silica. Over time these pockets crystallize and harden. The process will often create ring-like formations similar to those found in woody plants. Sometimes the formation process will create stalagtite type growths of crystal, which extend like fingers into the inner hollow of the bubble. These formations are rarer and can be exciting to find.
A common mistake new thunder egg hunters make is to plunge in with little understanding of where to find these treasures. Our first time out, our children began hacking away in the hardened obsidian and basalt layers of the rock walls. This approach is inadvisable for two reasons: firstly, the undermining of the rock face can all too easily result in a rockslide that could quickly end a pleasant family outing of geologic wonderment. Secondly, the best thunder eggs can often be found buried in the loose tuff and sandy ash debris located at foot level of the mining area. Please take precautions when “mining” for these “eggs” and follow any specific instructions given by the coordinators of the area in which you are digging.
While there are a number of different sites where you can “mine for these “eggs”, our earth cache brings you close to a site in the Madras area which is home to the Priday agate beds. There is no need to purchase anything to obtain this earth cache. Our coordinates bring you to a mining operation, which allows you to access mining beds where you can find these thunder eggs. It is free to camp, shower and access the sites; however, if you wish to keep what you have harvested, the prices are reasonable. At the time of posting, our family carried away 6 eggs, including 2 cut, for 6 dollars. You are allowed free use of picks, however, if you lose one, there is a steep cost…
In order to log this earth cacne, you must answer the following questions and post a picture of you and/or your group with GPS digging for thunder eggs:
1.) At coordinates N44 43.540 W120 55.428, there is a large rock formation. What kind of rock do you think this may be?
2.) What is the cost of failing to return your pick to the “establishment”?
We hope you have as much fun obtaining your thunder eggs as our family did! If you are able, please feel free to post a pic of your thunder eggs.
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